Backport of filesystem functions, don't cache unknown function results into v1.14

[github-actions]

Backport

This PR is auto-generated from #37810 to be assessed for backporting due to the inclusion of the label 1.14-backport.

The below text is copied from the body of the original PR.

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The CheckPrior function results validation did not take into account unknown values, because unknown values were not originally allowed in the plugin protocol from which this check was adapted.

The test is simple, in that we can just reverse the check which originally didn't allow this change in value. Provider function return values types are defined by the protocol, and should be validated at that call site. The CheckPrior code paths should only be used for the exact purpose of detecting invalid changes in the return value between successive phases of execution.

Fixes #37807

Target Release

1.13.x, 1.14

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

CHANGELOG entry

• This change is user-facing and I added a changelog entry.
• This change is not user-facing.

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Overview of commits

• 2227441

[github-actions]

Changelog Warning

Currently this PR would target a v1.14 release. Please add a changelog entry for in the .changes/v1.14 folder, or discuss which release you'd like to target with your reviewer. If you believe this change does not need a changelog entry, please add the 'no-changelog-needed' label.

[jbardin]

Holding on merging this for now, since v1.14 is in the RC phase. We can either merge into an rc2 or v1.14.1.