Merge bitcoin/bitcoin#24789: init, index: disallow indexes when running reindex-chainstate

dac44fc06ff9938d070aa5221d106a7f31da9d81 init: disallow reindex-chainstate with optional indexes (Martin Zumsande)
62e14285f95d4ecb9528813acca975640dd7c598 doc: Add note that -reindex will rebuild optional indexes (Martin Zumsande)

Pull request description:

  When started together with `-reindex-chainstate`, currently coinstatsindex gets corrupted and the blockfilterindex flatfiles duplicated. See the OP of #24630 for more a more detailed explanation on why this happens.

  This is an alternative to #24630 which does not wipe and rebuild the indexes but returns an `InitError` when they are activated, thus requiring the user to deactivate them temporarily until the `-reindex-chainstate` run is finished.

  This also disallows `-reindex-chainstate` in combination with `-txindex`, which is not leading to corruption, but currently still rebuilds the index unnecessarily and unexpectedly.

  As a long-term goal, it would be desirable to have the indexes tolerate `reindex-chainstate` by ignoring their `BlockConnected` notifications (there is discussion in #24630 about this) or possibly move `reindex-chainstate` option  into a `bitcoin-chainstate` executable, which could also solve the problem. But these would be larger projects - until then, it might be better to disallow the interaction than having corrupted indexes.

  The first commit adjusts the `-reindex` doc to mention that this option does rebuild all active indexes.

ACKs for top commit:
  ryanofsky:
    Code review ACK dac44fc06ff9938d070aa5221d106a7f31da9d81. Just fixed IsArgSet call and edited error messages since last review

Tree-SHA512: c1abf7d350648ae227c3fd6c95d9a54c3bac9de70915275dea1c87cca6d9a76a056c0e306d95ef8cfe4df1f8525b418e0e7a4f52ded3be464041c0dc297f8930

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