Add bionic mount points under /bionic

This change adds following files and symlinks:

Files:
/bionic/lib[64]/lib{c|dl|m}.so
/bionic/bin/linker[64]

Symlinks:
/system/lib[64]/lib{c|dl|m}.so -> /bionic/lib[64]/lib{c|dl|m}.so
/system/bin/linker[64] -> /bionic/bin/linker[64]
/system/bin/linker_asan[64] -> /bionic/bin/linker[64]

The files serve as mount points for either the bootstrap Bionic or the
default Bionic from the runtime APEX. init does the bind-mounting during
booting.

The symlinks are there to not change the ordinary paths to the bionic
files; there are many places that the paths are implied or hard-coded,
e.g., dlopen("/system/lib/libc.so") or DT_INTERP pointing to
/system/bin/linker in the vendor prebuilts.

Bug: 120266448
Test: m blueline, cf_x86, aosp_arm
The aforementioned files and symlinks are found

Change-Id: I97e38c29409ac0610dde285db8df6e94a7930094