Suppress E2E test suite slack notifications

[peterwilsoncc]

The E2E test suite is currently flakey and resulting in a lot of noise in the #core Slack channel. Despite efforts to resolve the flakiness, the issue remains.

I propose to suppress the E2E test notifications in Slack until the issue can be resolved. This is to account for the human condition, the Slack notifications are being seen as busyness that can be ignored.

https://core.trac.wordpress.org/ticket/58779

[peterwilsoncc]

In 56198:

Build/Test Tools: Suppress E2E test suite Slack notifications.

Remove Slack notifications of E2E test suite failures while the tests are flakey to improve the signal-to-noise ratio.

Fixes #58779.

Merged r56198 / ​https://github.com/WordPress/wordpress-develop/commit/0c5e0dfd7c0be04d4aac2c1dd236438b97a06d19

[desrosj]

In 56308:

Build/Test Tools: Restore automatically retrying failed E2E tests once.

This restores the GitHub Actions job responsible for automatically retrying a failed workflow once within the E2E testing workflow.

[56198] disabled Slack notifications for this workflow because of the increased number of timeout errors occurring after recent changes until they could be further investigated. Even though the signal-to-noise ration was way too high, there’s still benefit in retrying the workflow once to see if the timeout can be resolved without human intervention. The one retry attempt will not result in any Slack notifications.

Follow up to [56198].
See #58779.

[desrosj]

In 56539:

Build/Test Tools: Restore automatically retrying failed E2E tests once.

This restores the GitHub Actions job responsible for automatically retrying a failed workflow once within the E2E testing workflow.

[56198] disabled Slack notifications for this workflow because of the increased number of timeout errors occurring after recent changes until they could be further investigated. Even though the signal-to-noise ration was way too high, there’s still benefit in retrying the workflow once to see if the timeout can be resolved without human intervention. The one retry attempt will not result in any Slack notifications.

Follow up to [56198].
Merges [56308] to the 6.3 branch.
See #58779.

[SergeyBiryukov]

Follow-up: #58780, #59517.