feat(Data/Seq): modify and set operations for Seq

[vasnesterov]

Introduce modify and set operations for sequences, along with a few lemmas about them.

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• depends on: [Merged by Bors] - refactor(Data/Seq): reorganize Seq.lean #20071

[github-actions]

messageFile.md

[github-actions]

PR summary 2d46e13f91

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

+ modify
+ modify_cons_succ
+ modify_cons_zero
+ modify_nil
+ set
+ set_cons_succ
+ set_cons_zero
+ set_dropn_stable_of_lt
+ set_get_of_not_terminated
+ set_get_of_terminated
+ set_get_stable
+ set_nil

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).

[mathlib4-dependent-issues-bot]

This PR/issue depends on:

• [Merged by Bors] - refactor(Data/Seq): reorganize Seq.lean #20071
  By Dependent Issues (🤖). Happy coding!

[b-mehta]

This looks like a non-terminal simp, can we write it using simpa instead?

[b-mehta]

Suggested change

	have (i : ℕ) : (Function.update s.val n ((s.get? n).map f)) i = none ↔ s.get? i = none := by
	have (i : ℕ) : Function.update s.val n ((s.get? n).map f) i = none ↔ s.get? i = none := by

I haven't tested this, but it looks like it should work

[vasnesterov]

This PR has been migrated to a fork-based workflow: #26120