Merge bitcoin/bitcoin#28721: multiprocess compatibility updates

3b70f7b6156cb110c47a6e482791cf337bb6ad6d doc: fix broken doc/design/multiprocess.md links after #24352 (Ryan Ofsky)
6d43aad742c7ea28303cf2799528188938e7ce32 span: Make Span template deduction guides work in SFINAE context (Ryan Ofsky)
8062c3bdb9dd3062597ed8299e99151b612d32b7 util: Add ArgsManager SetConfigFilePath method (Ryan Ofsky)
441d00c60f0a67889d23f8556190ff99dde488bc interfaces: Rename CalculateBumpFees methods to be compatible with capn'proto (Ryan Ofsky)
156f49d682ef025fb942c997a6c5475e18eef9cf interfaces: Change getUnspentOutput return type to avoid multiprocess segfault (Ryan Ofsky)
4978754c0058bbdfbcd492f25fa49ef211e11d6e interfaces: Add schedulerMockForward method so mockscheduler RPC can work across processes (Ryan Ofsky)
924327eaf3ada45a603e80aa4a3ab38a0f8c8673 interfaces: Fix const virtual method that breaks multiprocess support (Ryan Ofsky)
82a379eca8251c736b4de6e7a2516582641ce397 streams: Add SpanReader ignore method (Russell Yanofsky)

Pull request description:

  This is a collection of small changes to interfaces and code which were needed as part of multiprocess PR #10102, but have been moved here to make that PR smaller.

  All of these changes are refactoring changes which do not affect behavior of current code

  ---

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/issues/28722).

ACKs for top commit:
  achow101:
    ACK 3b70f7b6156cb110c47a6e482791cf337bb6ad6d
  naumenkogs:
    ACK 3b70f7b6156cb110c47a6e482791cf337bb6ad6d
  maflcko:
    re-ACK 3b70f7b6156cb110c47a6e482791cf337bb6ad6d  🎆

Tree-SHA512: 2368772b887056ad8a9f84c299cfde76ba45943770e3b5353130580900afa9611302195b899ced7b6e303b11f053ff204cae7c28ff4e12c55562fcc81119ba4c

1 files changed, 4 insertions, 4 deletions

diff --git a/doc/design/multiprocess.md b/doc/design/multiprocess.md
index e6a77dbbc0..45681d12de 100644
--- a/doc/design/multiprocess.md
+++ b/doc/design/multiprocess.md
@@ -19,7 +19,7 @@ The `-debug=ipc` command line option can be used to see requests and responses b
 
 ## Installation
 
-The multiprocess feature requires [Cap'n Proto](https://capnproto.org/) and [libmultiprocess](https://github.com/chaincodelabs/libmultiprocess) as dependencies. A simple way to get starting using it without installing these dependencies manually is to use the [depends system](../depends) with the `MULTIPROCESS=1` [dependency option](../depends#dependency-options) passed to make:
+The multiprocess feature requires [Cap'n Proto](https://capnproto.org/) and [libmultiprocess](https://github.com/chaincodelabs/libmultiprocess) as dependencies. A simple way to get starting using it without installing these dependencies manually is to use the [depends system](../../depends) with the `MULTIPROCESS=1` [dependency option](../../depends#dependency-options) passed to make:
 
 ```
 cd <BITCOIN_SOURCE_DIRECTORY>
@@ -32,12 +32,12 @@ BITCOIND=bitcoin-node test/functional/test_runner.py
 
 The configure script will pick up settings and library locations from the depends directory, so there is no need to pass `--enable-multiprocess` as a separate flag when using the depends system (it's controlled by the `MULTIPROCESS=1` option).
 
-Alternately, you can install [Cap'n Proto](https://capnproto.org/) and [libmultiprocess](https://github.com/chaincodelabs/libmultiprocess) packages on your system, and just run `./configure --enable-multiprocess` without using the depends system. The configure script will be able to locate the installed packages via [pkg-config](https://www.freedesktop.org/wiki/Software/pkg-config/). See [Installation](https://github.com/chaincodelabs/libmultiprocess#installation) section of the libmultiprocess readme for install steps. See [build-unix.md](build-unix.md) and [build-osx.md](build-osx.md) for information about installing dependencies in general.
+Alternately, you can install [Cap'n Proto](https://capnproto.org/) and [libmultiprocess](https://github.com/chaincodelabs/libmultiprocess) packages on your system, and just run `./configure --enable-multiprocess` without using the depends system. The configure script will be able to locate the installed packages via [pkg-config](https://www.freedesktop.org/wiki/Software/pkg-config/). See [Installation](https://github.com/chaincodelabs/libmultiprocess/blob/master/doc/install.md) section of the libmultiprocess readme for install steps. See [build-unix.md](../build-unix.md) and [build-osx.md](../build-osx.md) for information about installing dependencies in general.
 
 ## IPC implementation details
 
 Cross process Node, Wallet, and Chain interfaces are defined in
-[`src/interfaces/`](../src/interfaces/). These are C++ classes which follow
+[`src/interfaces/`](../../src/interfaces/). These are C++ classes which follow
 [conventions](../developer-notes.md#internal-interface-guidelines), like passing
 serializable arguments so they can be called from different processes, and
 making methods pure virtual so they can have proxy implementations that forward
@@ -58,7 +58,7 @@ actual serialization and socket communication.
 As much as possible, calls between processes are meant to work the same as
 calls within a single process without adding limitations or requiring extra
 implementation effort. Processes communicate with each other by calling regular
-[C++ interface methods](../src/interfaces/README.md). Method arguments and
+[C++ interface methods](../../src/interfaces/README.md). Method arguments and
 return values are automatically serialized and sent between processes. Object
 references and `std::function` arguments are automatically tracked and mapped
 to allow invoked code to call back into invoking code at any time, and there is