sdk-base: add `Room::pinned_events(&self)` #10555

Job	Run time
Generate Crypto FFI Apple XCFramework	8m 2s
Run Complement Crypto tests / tests	9m 46s
xtask / xtask-🐧	10s
xtask / xtask-🍏	9s
matrix-rust-components-kotlin	5m 40s
matrix-rust-components-swift	10m 32s
Test UniFFI bindings generation	3m 2s
	37m 21s

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