Improve handling of rates when converting to timecode strings #2265

Job	Run time
cpp_build (ubuntu-latest)	1m 41s
py_build_test (ubuntu-latest, 3.7)	30s
cpp_build (windows-latest)	1m 48s
py_build_test (ubuntu-latest, 3.8)	20s
cpp_build (macos-13)	4m 27s
py_build_test (ubuntu-latest, 3.9)	28s
cpp_build (macos-latest)	1m 56s
py_build_test (ubuntu-latest, 3.10)	25s
py_build_test (ubuntu-latest, 3.11)	20s
py_build_test (ubuntu-latest, 3.12)	23s
py_build_test (windows-latest, 3.7)	2m 25s
py_build_test (windows-latest, 3.8)	1m 38s
py_build_test (windows-latest, 3.9)	1m 25s
py_build_test (windows-latest, 3.10)	1m 40s
py_build_test (windows-latest, 3.11)	1m 14s
py_build_test (windows-latest, 3.12)	1m 24s
py_build_test (macos-13, 3.7)	1m 3s
py_build_test (macos-13, 3.8)	40s
py_build_test (macos-13, 3.9)	1m 1s
py_build_test (macos-13, 3.10)	36s
py_build_test (macos-13, 3.11)	55s
py_build_test (macos-13, 3.12)	1m 24s
py_build_test (macos-latest, 3.10)	28s
py_build_test (macos-latest, 3.11)	26s
py_build_test (macos-latest, 3.12)	30s
py_build_test (windows-latest, mingw64, msys2)	2m 13s
package_sdist	0s
package_wheels	0s
	31m 20s

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