Remove more Gecko-internal enums/dicts from WebIDL #1570

Job	Run time
build_nightly	1m 40s
Check	1m 8s
build_benchmarks	55s
build_examples	3m 35s
Verify that web-sys is compiled correctly	53s
Clippy	5m 25s
dist_linux_aarch64_gnu	2m 48s
dist_linux_x86_64_musl	2m 31s
dist_macos_aarch64	4m 1s
dist_macos_x86_64	4m 7s
dist_windows	3m 0s
doc_api	1m 12s
doc_book	13s
Rustfmt	14s
Build and test the deno example	50s
Run js-sys crate tests	2m 2s
Run native tests	1m 48s
Run wasm-bindgen crate tests with multithreading enabled	1m 32s
Test TypeScript output of wasm-bindgen	1m 7s
Run UI compile-fail tests	4m 34s
Run wasm-bindgen crate tests (unix)	7m 19s
Run web-sys crate tests	3m 58s
Run wasm-bindgen-webidl crate tests	2m 10s
test_examples	2m 31s
deploy	1m 55s
	1h 1m 28s

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