fix: misc issues with unified expression filter

[AdityaHegde]

Fixing issues with the unified expression filter changes.

1. Refreshing a canvas with filters doesnt add the filter anymore. Was missing metricsViewsProvider.ready check.
2. Removing an empty filter doesnt remove the pill. Needs an explicit handling since it doesnt go through expr change cycle.
3. Fix canvas reports not forwarding canvasStateOverride

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!

[nishantmonu51]

Could we replay pending filter params once metricsViewsProvider.ready becomes true? The report editor uses CanvasProvider with isolated/urlStateOverride without CanvasDashboardWrapper, so there is no syncStoreWithSource to recover the skipped update. With cached dimension specs and a pending time summary, saved filters remain missing after readiness; a targeted test fails with this guard and passes when only the guard is removed. Saving can then drop the captured metricsViewFilters used for report row restrictions. Please cover this isolated report-editor path.

[AdityaHegde]

Doing a narrow fix for now by adding a simple component that replays for reports. Will standardise this once time controls have been moved in my other PR