0bc9d354df multi_index: fix compilation failure with boost >= 1.91 (Cory Fields)
Pull request description:
This effectively reverts a3cb309e7c from PR #30194.
That PR reduced the `multi_index` type signatures as recommended upstream, but this is no longer supported as of boost 1.91 because it is no longer necessary. 1.91 drops support for the pre-c++11 work-arounds that bloated the type signatures to begin with.
The upstream `BOOST_MULTI_INDEX_ENABLE_MPL_SUPPORT` define is meant to provide compatibility with removed features, but it does not work for this case. Using `indexed_by` directly when defining the `multi_index` (as opposed to inheriting from it) works with all versions, and avoids the use of the back-compat define.
This is a slight regression when building against boost < 1.91 because the bloated type signatures are reintroduced in that case, but it's not significant enough to go to the trouble of introducing version detection and ifdefs.
ACKs for top commit:
maflcko:
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ACK 0bc9d354df.
w0xlt:
ACK 0bc9d354df
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