Backport of #26343 to release/v7.6

Dependencies

This PR depends on #26490 being merged first.

PR #26490 backports prerequisite changes that this PR builds upon. Please review and merge #26490 before merging this PR.

---

Triggered by @TravisEz13 on behalf of @daxian-dbw

Original CL Label: CL-General

/cc @PowerShell/powershell-maintainers

Impact

REQUIRED: Choose either Tooling Impact or Customer Impact (or both). At least one checkbox must be selected.

Tooling Impact

• Required tooling change
• Optional tooling change (include reasoning)

Customer Impact

• Customer reported
• Found internally

This makes the PSFeedbackProvider experimental feature stable by removing it from the experimental features list and removing the old suggestion framework. This is a customer-facing change as it affects how feedback/suggestions are presented to users in the console.

Regression

REQUIRED: Check exactly one box.

• Yes
• No

This is not a regression.

Testing

Original PR was tested on master branch. Backport verified by successfully resolving merge conflicts while preserving v7.6-specific experimental features, cherry-pick completed successfully, and 4 files changed with clean removal of deprecated code.

Risk

REQUIRED: Check exactly one box.

• High
• Medium
• Low

This is a feature graduation that has been approved by PMs and maintainers. The PSFeedbackProvider feature has been tested as experimental and is now being made stable. The old suggestion framework removal is a cleanup of deprecated code. The conflicts were straightforward - preserving v7.6 experimental features while removing PSFeedbackProvider.

Merge Conflicts

Conflicts occurred in 2 files during cherry-pick:

src/System.Management.Automation/engine/ExperimentalFeature/ExperimentalFeature.cs

• Conflict: Release branch v7.6 contains additional experimental features (PSNativeWindowsTildeExpansion, PSRedirectToVariable) not present in main
• Resolution: Removed PSFeedbackProvider constant and registration as per the PR, while preserving v7.6-specific experimental features

src/System.Management.Automation/engine/hostifaces/HostUtilities.cs

• Conflict: Old suggestion framework code that the PR removes still exists in v7.6
• Resolution: Cleanly removed all deprecated suggestion framework methods (GetSuggestion and supporting code) as intended by the PR