feat(FieldTheory/KrullTopology): generalize theorems

[plp127]

Simultaneously generalize IntermediateField.fixingSubgroup_isClosed and InfiniteGalois.fixingSubgroup_isClosed to algebraic extensions.

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[github-actions]

PR summary a99960b7a0

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

+ IntermediateField.isClosed_fixingSubgroup

You can run this locally as follows

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

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

The doc-module for scripts/pr_summary/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/reporting/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).

[vihdzp]

I've made some minor suggestions which are mostly unrelated to the PR. Otherwise LGTM

[vihdzp]

This seems more important than the docstring is giving it credit for.

Suggested change

	/-- The Galois correspondence from intermediate fields to closed subgroups. -/
	/-- The **Galois correspondence** from intermediate fields to closed subgroups. -/

[plp127]

closing in favor of #36239