mock: backport `tracing-mock` to v0.1.x #5416

Job	Run time
cargo check	38s
cargo check (+MSRV -Zminimal-versions)	0s
cargo test (${{ matrix.rust }} on ${{ matrix.os }})	0s
cargo fmt	0s
cargo check (feature combinations)	0s
cargo test (wasm)	0s
build tests (wasm)	0s
cargo test (feature-specific)	0s
warnings	0s
all systems go!	0s
	38s

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