feat: add TLeafC - string - writing support #2725

Job	Run time
build (windows-latest, 3.8)	9m 45s
vanilla-build (windows-latest, 3.11)	5m 2s
build (windows-latest, 3.9)	8m 1s
vanilla-build (ubuntu-latest, 3.11)	2m 43s
build (windows-latest, 3.10)	8m 0s
vanilla-build (macos-latest, 3.11)	6m 21s
build (macos-latest, 3.7)	6m 55s
build (macos-latest, 3.8)	6m 56s
build (macos-latest, 3.9)	7m 23s
build (macos-latest, 3.10)	9m 19s
build (ubuntu-latest, 3.7)	3m 28s
build (ubuntu-latest, 3.8)	15m 12s
build (ubuntu-latest, 3.9)	3m 27s
build (ubuntu-latest, 3.10)	3m 19s
	1h 35m 51s

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