Moved `xml` definitions to `atspi-common` #580

Job	Run time
find-msrv	3s
rustfmt	9s
no-unused-dependencies	20s
wasm-compatible-common-crate	33s
nightly Clippy	58s
benchmarks	2m 27s
coverage	1m 28s
rustdoc	44s
msrv-compliance	1m 14s
semver-compliance	1m 14s
tests	2m 9s
	11m 19s

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