Adopt towncrier for changelogs #21500

Job	Run time
Run Complement Crypto tests / tests	26s
xtask / xtask-🐧	10s
xtask / xtask-🍏	28s
Generate Crypto FFI Apple XCFramework	-1s
Test UniFFI bindings generation	1s
matrix-rust-components-swift	1s
matrix-rust-components-kotlin	1s
	1m 6s

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