Tests

add TxPartition::{first, last}_key_value #521

Job	Run time
test (stable, ubuntu-latest)	3m 4s
examples (stable, ubuntu-latest)	5m 48s
test (stable, windows-latest)	6m 30s
examples (stable, windows-latest)	8m 30s
cross (aarch64-unknown-linux-gnu)	2m 56s
test (stable, macos-latest)	2m 35s
examples (stable, macos-latest)	6m 7s
cross (aarch64-unknown-linux-musl)	3m 20s
test (1.74.0, ubuntu-latest)	3m 20s
examples (1.74.0, ubuntu-latest)	6m 8s
cross (i686-unknown-linux-gnu)	1m 51s
test (1.74.0, windows-latest)	5m 31s
examples (1.74.0, windows-latest)	8m 45s
cross (powerpc64-unknown-linux-gnu)	2m 41s
test (1.74.0, macos-latest)	2m 53s
examples (1.74.0, macos-latest)	6m 12s
cross (riscv64gc-unknown-linux-gnu)	3m 7s
	1h 19m 18s

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