feat(finiteness): support finiteness [h, h'] syntax

[grunweg]

This PR adds support for the finiteness [h, h'] syntax. This can be combined with the existing versions, such as supporting aesop clauses or the finiteness? and finiteness_nonterminal variants. This allows golfing mathlib in a few places.

While adding tests, we take the opportunity to also test finiteness? and adding aesop clauses: these were previously untested. We also improve the tactic doc-string slightly: making it fully confirm to the new style guidelines is left for a future PR.

This PR is inspired by #30388.

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[grunweg]

@fpvandoorn We discussed this briefly. @Vierkantor in case you'd like to look at the new doc-string formatting (entirely optional --- but it would be good to land this PR before polishing finiteness' doc-string).

[github-actions]

PR summary d498a88e35

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).