Rename feature gate files to use gate names

[tengqm]

The conversion to/from snake-case was not necessary and it is causing mental burden and extra labor in resyncing changes.

Description

Issue

Closes: #

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[sftim]

IMO, you must also update the contributor docs when making this change @tengqm.

Missing that out means we can't / shouldn't merge this, no matter how frustrated you feel about the matter.

[tengqm]

@sftim #47863