Merge #16805: logs: add timing information to FlushStateToDisk()

dcef9a2922317cb2849f397366b6c56d755db6c9 logs: add timing information to FlushStateToDisk() (James O'Beirne)
41edaf227a69bc4846d5996675e8763fdfe0f367 logs: add BCLog::Timer and related macros (James O'Beirne)

Pull request description:

  It's currently annoying to detect FlushStateToDisk() calls when benchmarking since they have to be inferred from a drop in coins count from the `UpdateTip: ` log messages. This adds a new logging utility, `BCLog::Timer`, and some related macros that are generally useful for printing timing-related logging messages, and a message that is unconditionally written when the coins cache is flushed to disk.

  ```
  2019-09-04T20:17:51Z FlushStateToDisk: write block and undo data to disk completed (3ms)
  2019-09-04T20:17:51Z FlushStateToDisk: write block index to disk completed (370ms)
  2019-09-04T20:17:51Z FlushStateToDisk: write coins cache to disk (2068451 coins, 294967kB) completed (21481ms)
  ```

ACKs for top commit:
  laanwj:
    Thanks, ACK dcef9a2922317cb2849f397366b6c56d755db6c9
  ryanofsky:
    Code review ACK dcef9a2922317cb2849f397366b6c56d755db6c9. No changes since last review other than moving code to new timer.h header

Tree-SHA512: 6d61e48a062d3edb48d0e056a6f0b1f8031773cc99289ee4544f8349d24526b88519e1e304009d56e428f1eaf76c857bf8e7e1c0b6873a6f270306accb5edc3d

1 files changed, 1 insertions, 0 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 8308388331..ff4f071a3c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -146,6 +146,7 @@ BITCOIN_CORE_H = \
   dbwrapper.h \
   limitedmap.h \
   logging.h \
+  logging/timer.h \
   memusage.h \
   merkleblock.h \
   miner.h \