Add libm_alias_finite for _finite symbols

This patch adds a new macro, libm_alias_finite, to define all _finite
symbol.  It sets all _finite symbol as compat symbol based on its first
version (obtained from the definition at built generated first-versions.h).

The <fn>f128_finite symbols were introduced in GLIBC 2.26 and so need
special treatment in code that is shared between long double and float128.
It is done by adding a list, similar to internal symbol redifinition,
on sysdeps/ieee754/float128/float128_private.h.

Alpha also needs some tricky changes to ensure we still emit 2 compat
symbols for sqrt(f).

Passes buildmanyglibc.

Co-authored-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>