[Python] Add clear method for builder reuse #5807

Job	Run time
Build Linux with out-of-source build location	24s
Build Linux C++ (11, g++-13)	34s
Build Linux (g++-13)	32s
Build Linux C++ (11, clang++-15)	27s
Build Linux (clang++-15)	32s
Build Linux C++ (14, g++-13)	27s
Build Linux C++ (14, clang++-15)	40s
Build Android (on Linux)	2m 35s
Build Linux C++ (17, g++-13)	35s
Build Benchmarks (on Linux) (g++-13)	1m 27s
Build Linux C++ (17, clang++-15)	27s
Build Linux C++ (20, g++-13)	28s
Build Windows C++ (11)	3m 17s
Build Dart	38s
Build Windows C++ (14)	3m 48s
Build .NET Windows	23s
Build Windows C++ (17)	3m 50s
Build .NET Windows (-p:UnsafeByteBuffer=true)	23s
Check Generated Code (g++-13)	16s
Build Windows C++ (20)	5m 22s
Build Linux C++ (20, clang++-15)	29s
Check Generated Code (clang++-15)	17s
Build Windows C++ (23)	5m 26s
Build Linux C++ (23, g++-13)	28s
Check Generated Code on Windows	4m 43s
Build Go	52s
Build Java	9s
Build Kotlin Linux	1m 46s
Build Kotlin MacOS	5m 43s
Build Linux with -DFLATBUFFERS_NO_FILE_TESTS	26s
Build Mac (for Intel)	2m 38s
Build Mac (universal build)	2m 8s
Build Nim	23s
Build PHP	16s
Build Python	26s
Build Rust Linux	1m 6s
Build Rust Windows	1m 23s
Build Swift	1m 9s
Build Swift Wasm	1m 5s
Build TS	43s
Build Windows 2019	4m 8s
Build Windows 2015	3m 17s
Build Windows 2017	3m 44s
release-digests	0s
provenance	0s
	1h 9m 50s

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