Improve IME area reporting and set IME area in `TextArea` #2410

Job	Run time
cargo check (aarch64-android)	40s
cargo check (msrv) (windows-latest)	3m 19s
cargo clippy (windows-latest)	6m 6s
cargo check (msrv) (wasm32)	32s
cargo check (msrv) (macos-latest)	1m 14s
cargo clippy (wasm32)	2m 2s
cargo check (msrv) (ubuntu-latest)	59s
cargo clippy (macos-latest)	2m 24s
cargo clippy (ubuntu-latest)	3m 33s
cargo doc	51s
Prime LFS Cache	40s
formatting	28s
cargo test (wasm32)	46s
typos	5s
cargo test (windows-latest)	4m 29s
cargo test (macos-latest)	1m 46s
cargo test (ubuntu-latest)	3m 53s
	33m 47s

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