Add `ts2str` and `ts2timestr` (#133) #363

Job	Run time
rust_clippy_check_windows	1m 42s
rustfmt_check (macos-latest)	24s
build_dynamic_and_test_windows_pre	6m 15s
build_static_and_test_ubuntu (release/6.0, nightly, no valgrind)	5m 45s
rustfmt_check (windows-latest)	51s
docs_rs_check	1m 8s
build_static_and_test_ubuntu (release/6.0, 1.70.0, no valgrind)	5m 48s
rustfmt_check (ubuntu-latest)	12s
rust_clippy_check_ubuntu	5m 3s
build_static_and_test_ubuntu (release/6.1, nightly, valgrind)	1h 3m 37s
build_static_and_test_ubuntu (release/6.1, nightly, no valgrind)	6m 47s
build_static_and_test_ubuntu (release/6.1, 1.70.0, no valgrind)	6m 11s
build_dynamic_and_test_windows (nightly)	2m 13s
build_dynamic_and_test_windows (1.70.0)	2m 12s
	1h 48m 8s

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