rename local functions with `_`s
rename local functions with `_`s

These will be flagged by the next linter release which updates `non_constant_identifier_names` to flag local functions.

Change-Id: I873400f61748a145f3c2a6630a21bcd1975c309c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/242503
Reviewed-by: Alexander Aprelev <dfb74c35a357c2059971a4bf7fe26b6a7c18085d@google.com>
Commit-Queue: Phil Quitslund <3faecbdd7b7be83f493f037bf1d597e6bb9d0848@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk