Flip incompatible_exclusive_test_sandboxed

[gasparev]

Solves #3791 #16871 bazel-contrib/SIG-rules-authors#40
Steps to do before merging:

• Bazel checks green Build with incompatible_exclusive_test_sandboxed #16868
• Downstream projects green https://buildkite.com/bazel/bazelisk-plus-incompatible-flags/builds/1348

[coeuvre]

Thanks for your PR!

There are hundreds tests inside google which rely on the old behaviour (that's why I added this flag instead of making the changes directly in #3791) so we can't just merge this PR without doing anything internally.

I can't migrate all the internal tests because of workload. To move this PR forward, I will try to disable this flag internally first.

[gasparev]

Thanks @coeuvre

[gasparev]

Hey @coeuvre did you have time to check whether disabling the flag internally works?

[coeuvre]

Internally we disabled this flag, and so far, everything looks good. (In case of something go wrong, I probably need to rollback this change).