Invariant: prevent a deleted account from leaving (most) artifacts on the ledger. (#4663)

* Add feature / amendment "InvariantsV1_1"

* Adds invariant AccountRootsDeletedClean:

* Checks that a deleted account doesn't leave any directly
  accessible artifacts behind.
* Always tests, but only changes the transaction result if
  featureInvariantsV1_1 is enabled.
* Unit tests.

* Resolves #4638

* [FOLD] Review feedback from @gregtatcam:

* Fix unused variable warning
* Improve Invariant test const correctness

* [FOLD] Review feedback from @mvadari:

* Centralize the account keylet function list, and some optimization

* [FOLD] Some structured binding doesn't work in clang

* [FOLD] Review feedback 2 from @mvadari:

* Clean up and clarify some comments.

* [FOLD] Change InvariantsV1_1 to unsupported

* Will allow multiple PRs to be merged over time using the same amendment.

* fixup! [FOLD] Change InvariantsV1_1 to unsupported

* [FOLD] Update and clarify some comments. No code changes.

* Move CMake directory

* Rearrange sources

* Rewrite includes

* Recompute loops

* Fix merge issue and formatting

---------

Co-authored-by: Pretty Printer <cpp@ripple.com>

src/xrpld/app/misc/FeeVoteImpl.cpp

@@ -277,9 +277,9 @@ FeeVoteImpl::doVoting(
     }
 
     // choose our positions
-    // TODO: Use structured binding once LLVM issue
-    // https://github.com/llvm/llvm-project/issues/48582
-    // is fixed.
+    // TODO: Use structured binding once LLVM 16 is the minimum supported
+    // version. See also: https://github.com/llvm/llvm-project/issues/48582
+    // https://github.com/llvm/llvm-project/commit/127bf44385424891eb04cff8e52d3f157fc2cb7c
     auto const baseFee = baseFeeVote.getVotes();
     auto const baseReserve = baseReserveVote.getVotes();
     auto const incReserve = incReserveVote.getVotes();