[Merged by Bors] - feat(List/Perm): add lemmas

[urkud]

• Add List.map_perm_map_iff and List.Perm.flatMap.
• Add some @[gcongr] and @[simp] attrs.
• Add Relation.comp_fun_eq and Relation.fun_eq_comp.

---

[github-actions]

PR summary 4b38037fe8

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff

+ Perm.flatMap
+ comp_eq_fun
+ eq_map_comp_perm
+ fun_eq_comp
+ map_perm_map_iff

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.

---

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).

[eric-wieser]

bors d+

Thanks!

[mathlib-bors]

✌️ urkud can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

[leanprover-community-mathlib4-bot]

As this PR is labelled auto-merge-after-CI, we are now sending it to bors:

bors merge

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

• Build
• Lint style