[BOLT] Add support for BOLT-reserved space in a binary (#90300)

Allow the user to allocate space in a binary that could be used by BOLT
for allocating new sections. The reservation is specified by two special
symbols recognizable by BOLT: __bolt_reserved_{start,end}.

The reserved space will be useful for optimizing the Linux kernel where
we cannot allocate a new executable segment. However, the support is not
limited to kernel binaries as some user-space application may find it
useful too.