refactor(Algebra/*): generalize of_ringEquiv lemmas

[urkud]

Some lemmas assumed that two modules over different rings
admit a semilinear equivalence with respect to a RingEquiv.
While this is mathematically equivalent
to the definition we use everywhere else
(a pair of RingHoms with RingHomInvPair assumptions),
it does not directly apply neither to the linear case,
nor to the starRingEnd case.

This PR drops of_ringEquiv theorems
and generalizes of_equiv theorems
to semilinear equivalences instead.

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[github-actions]

PR summary 99884c2730

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

+ Projective.of_equiv'
+ iff_of_equiv
+ of_ringEquiv_symm
+ toRingEquiv

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 scripts/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).