Feature request: Commit the search filter as a transform

I'd like to be able to "commit" the current search filter as a transform. This would push a transform and then clear the search field. This would let us "stack" multiple searches, and it would allow adding other transforms on top without accidentally dropping samples.

As for the UI, we could add a similar dropdown button like we have on the marker chart panel.

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Example profile: https://share.firefox.dev/4aoDUSt

In this profile, I have a search filter applied. Now I want to apply some "merge function" transforms to merge away the bottom frames in the flame graph. But after merging those functions, the samples will disappear! Because the search filter currently always applies at the end, after all the transforms are applied.
If I had the option to commit the search filter, then I could commit it first, and then add the "merge function" transforms, and all the samples would remain in view.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-1004)