Merge bitcoin/bitcoin#30605: Cluster linearization: separate tests from tests-of-tests

d7fca5c clusterlin: add big comment explaning the relation between tests (Pieter Wuille)
b64e61d clusterlin: abstract try-permutations into ExhaustiveLinearize function (Pieter Wuille)
1fa55a6 clusterlin tests: verify that chunks are minimal (Pieter Wuille)
da23ece clusterlin tests: support non-empty ReadTopologicalSubset() (Pieter Wuille)
94f3e17 clusterlin tests: compare with fuzz-provided linearizations (Pieter Wuille)
5f92ebe clusterlin tests: compare with fuzz-provided topological sets (Pieter Wuille)
6e37824 clusterlin tests: optimize clusterlin_simple_linearize (Pieter Wuille)
98c1c88 clusterlin tests: separate testing of SimpleLinearize and Linearize (Pieter Wuille)
10e90f7 clusterlin tests: make SimpleCandidateFinder always find connected (Pieter Wuille)
a38c389 clusterlin tests: separate testing of Search- and SimpleCandidateFinder (Pieter Wuille)
77a432e clusterlin tests: count SimpleCandidateFinder iterations better (Pieter Wuille)

Pull request description:

  Part of the cluster mempool project: #30289

  The current cluster linearization fuzz tests contain two tests which combine testing of production code with testing of the test code itself:
  * `clusterlin_search_finder`: establishes the correctness of `SearchCandidateFinder` by comparing against both `SimpleCandidateFinder` and `ExhaustiveCandidateFinder` (which is even more simple than `SimpleCandidateFinder`). If `SimpleCandidateFinder` works correctly, then this comparison with `ExhaustiveCandidateFinder` is redundant. If it isn't, we ought to find that in a test specific to `SimpleCandidateFinder` rather than as a side-effect of testing `SearchCandidateFinder`. Split this functionality out into a new `clusterlin_simple_finder`.
  * `clusterlin_linearize`: establishes the correctness of `Linearize` by comparing against both `SimpleLinearize` and literally every valid linearization for the cluster. Again, if `SimpleLinearize` works correctly, then this comparison with all valid linearizations is redundant, and if it isn't we should find it in a test for `SimpleLinearize`. Do so by splitting off that functionality into `clusterlin_simple_linearize`.

  After that, a few general improvements to the affected tests are made (comparing with linearizations and subsets read from the fuzz input, plus a performance improvement).

ACKs for top commit:
  marcofleon:
    Re ACK d7fca5c
  ismaelsadeeq:
    re-ACK d7fca5c
  monlovesmango:
    ACK d7fca5c

Tree-SHA512: 33cb76bd9b9547a5f3ee231fa452e928f064ad03af98e3d9e64246eb972f2b026c13e7367257ccdac1ae57982ee8ef98c907684588ecbb4bc4c82cbec160b3e8

Author: glozow