This is an implementation of this REAPI spec update:
https://github.com/bazelbuild/remote-apis/pull/213

Here's a bazel-remote build that can be used to test this change:
https://github.com/buchgr/bazel-remote/pull/527

Fixes #14654

Closes #14870.

PiperOrigin-RevId: 430167812
(cherry picked from commit d184e488

)

Co-authored-by: Mostyn Bramley-Moore <mostyn@antipode.se>