Combine the conversion of UTF-8 to bytes into a single base function #14510

Job	Run time
Sanity: Linux -Dusethreads	10m 22s
involved_authors_debug	8s
linux i386/ubuntu (-Dusedevel)	15m 33s
linux (-Uusethreads)	9m 27s
linux (-Duseshrplib -Dusequadmath -Dusecbacktrace -Dusethreads)	11m 8s
install	10m 26s
linux (-Duserelocatableinc)	9m 28s
Windows mingw64	33m 46s
linux (-Dcc='clang')	9m 55s
cygwin	2h 0m 8s
macOS (Monterey) 12 (-Uusethreads)	11m 29s
Windows msvc142	52m 54s
linux (-Dcc='g++')	9m 35s
linux (-Accflags=-DSILENT_NO_TAINT_SUPPORT)	9m 21s
macOS (Monterey) 12 (-Duseithreads -Duseshrplib)	13m 4s
ASAN (-Accflags=-DPURIFY)	21m 6s
linux (-Accflags=-DNO_TAINT_SUPPORT)	9m 21s
ASAN (-DDEBUGGING)	22m 49s
linux (-DDEBUGGING -Accflags=-DPERL_RC_STACK)	9m 35s
ASAN (-Dusethreads)	22m 32s
linux (-Uusedl)	9m 10s
dist Linux 5.38 -Dusethreads	2m 5s
dist Linux 5.38 -Uusethreads	2m 8s
Test dist/ modules on MacOS system perl	4m 22s
dist Linux 5.24 -Dusethreads	1m 50s
minitest	3m 37s
dist Linux 5.24 -Uusethreads	1m 52s
dist Linux 5.10 -Dusethreads	1m 47s
PERL_UNICODE (-Uusethreads)	8m 17s
PERL_UNICODE (-Dusethreads -Accflags=-DPURIFY -Dcc='gcc -fsanitize=address' -Dld='gcc -fsanitize=...	24m 23s
dist Linux 5.10 -Uusethreads	1m 51s
dist Linux 5.8 -Dusethreads	1m 56s
dist Linux 5.8 -Uusethreads	1m 56s
	7h 57m 21s

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