release-25.1: roachprod/roachtest/logictest: unconditionally disable Sentry crash reporting

[blathers-crl]

Backport 1/1 commits from #146343 on behalf of @srosenberg.

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Previously, the environment variable, COCKROACH_SKIP_ENABLING_DIAGNOSTIC_REPORTING=1 was used to disable both telemetry and crash reporting. However, the default for diagnostics.reporting.enabled has flipped from false to true as of [1]. The same PR added a regression wrt to the environment variable–it no longer disabled crash reporting via Sentry.

Recall, we prefer to disable Sentry crash reporting for all tests since our (internal) test artifacts contain a superset of contextual information; i.e., Sentry reports are of limited use for test failures; as such they add more noise than signal.

Also recall, unit tests effectively disable Sentry by not invoking cli.doMain, which invokes SetupCrashReporter. Both integration (docker) and roachtests rely on COCKROACH_SKIP_ENABLING_DIAGNOSTIC_REPORTING=1. Mixedversion logic tests until this change, simply assumed that diagnostics.reporting.enabled defaulted to false.

This change fixes the regression, introduced in [1], by correctly updating diagnostics.reporting.enabled to affect the environment variable. It also sets COCKROACH_CRASH_REPORTS to the empty string, which disables crash reporting before a server is fully initialized.

[1] #131097

Fixes: #145457
Epic: none
Release note: None

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Release justification: test-only change

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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Also, please add a brief release justification to the body of your PR to justify this
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[blathers-crl]

It looks like your PR touches production code but doesn't add or edit any test code. Did you consider adding tests to your PR?

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[cockroach-teamcity]

This change is 

[srosenberg]

TFTR!