Merge ElementsProject/rust-elements#264: transaction: tests: deserial… #643

Job	Run time
Check WASM	31s
Prepare	5s
Test - stable toolchain	2m 53s
Docs - stable toolchain (recent)	39s
Test - nightly toolchain	2m 41s
Test - MSRV	15m 35s
Lint - nightly toolchain (recent)	38s
Docs - nightly toolchain (recent)	42s
	23m 44s

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