fluent-bit: update to 5.0.8, adopt maintainer, fix musl startup segfault

fluent-bit: update to 5.0.8, adopt maintainer, fix musl startup segfault

Update 4.2.0 -> 5.0.8 and adopt maintainership. fluent-bit segfaulted at
startup on every musl target: under GCC 14 the upstream C-TLS probe no longer
compiles (undeclared __tls_get_addr), so the pthread_key fallback calls
pthread_getspecific() before pthread_key_create() and derefs a NULL tsd array
on musl (glibc is unaffected). Force -DFLB_HAVE_C_TLS=Yes for __thread TLS.

Signed-off-by: Alexandru Ardelean <redacted>