Convert `UseLetInEveryBoundCaseVariable` to be a formatter #306

Job	Run time
Test / Windows (5.9 - windows-2022)	9m 44s
Test / Windows (6.0 - windows-2022)	8m 31s
Test / Linux (5.8 - jammy)	2m 1s
Test / Windows (nightly - windows-2022)	11m 9s
Test / Linux (5.9 - jammy)	2m 8s
Test / Windows (nightly-6.1 - windows-2022)	14m 14s
Test / Linux (5.10 - jammy)	2m 11s
Test / Linux (6.0 - jammy)	2m 25s
Test / Linux (nightly-main - jammy)	4m 7s
Test / Linux (nightly-6.1 - jammy)	3m 53s
Soundness / API breakage check	3m 59s
Soundness / Broken symlinks check	3s
Soundness / Documentation check	2m 11s
Soundness / Format check	38s
Soundness / License headers check	0s
Soundness / Python lint check	5s
Soundness / Shell check	32s
Soundness / Unacceptable language check	5s
Soundness / YAML lint check	4s
	1h 8m 0s

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