Auto merge of #20676 - fabricedesre:ime-embedding, r=cbrewster

Notify the embedder when it should display or hide an IME

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This adds a couple of embedder messages triggered when an editable element is focused or blured. The embedder also gets the type of data to edit so it can display a different keyboard type or a custom input method eg. for color choosing.

This is a partial fix for issue #12127

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- [X] `./mach build -d` does not report any errors
- [X] `./mach build-geckolib` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because there are no tests for the embedding api :(

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