[Swift] Sets Swift minimum support to 5.8 #5923

Job	Run time
Build Dart	45s
Build Benchmarks (on Linux) (g++-13)	1m 57s
Build Android (on Linux)	3m 7s
Build Windows C++ (11)	3m 25s
Build Windows C++ (14)	3m 52s
Build Windows C++ (17)	3m 56s
Build .NET Windows	1m 42s
Check Generated Code (g++-13)	42s
Check Generated Code on Windows	4m 2s
Build .NET Windows (-p:UnsafeByteBuffer=true)	48s
Build Windows C++ (20)	5m 27s
Check Generated Code (clang++-15)	32s
Build Windows C++ (23)	5m 29s
Build Go	50s
Build Java	38s
Build Kotlin Linux	2m 13s
Build Kotlin MacOS	4m 4s
Build Linux (g++-13)	52s
Build Linux C++ (11, g++-13)	55s
Build Linux with -DFLATBUFFERS_NO_FILE_TESTS	51s
Build Linux (clang++-15)	55s
Build Linux with out-of-source build location	40s
Build Linux C++ (11, clang++-15)	41s
Build Mac (for Intel)	1m 42s
Build Linux C++ (14, g++-13)	46s
Build Nim	37s
Build Linux C++ (14, clang++-15)	48s
Build Mac (universal build)	5m 56s
Build Linux C++ (17, g++-13)	55s
Build PHP	21s
Build Python	22s
Build Linux C++ (17, clang++-15)	48s
Build Rust Linux	1m 11s
Build Linux C++ (20, g++-13)	58s
Build Rust Windows	1m 24s
Build Swift (5.8)	1m 4s
Build Swift Wasm	35s
Build Linux C++ (20, clang++-15)	54s
Build Swift (5.9)	1m 11s
Build Linux C++ (23, g++-13)	48s
Build TS	59s
Build Windows 2019	3m 59s
release-digests	0s
provenance	0s
	1h 13m 41s

Provide feedback