block, block-backend: write some hot coroutine wrappers by hand

The introduction of the graph lock is causing blk_get_geometry, a hot function
used in the I/O path, to create a coroutine.  However, the only part that really
needs to run in coroutine context is the call to bdrv_co_refresh_total_sectors,
which in turn only happens in the rare case of host CD-ROM devices.

So, write by hand the three wrappers on the path from blk_co_get_geometry to
bdrv_co_refresh_total_sectors, so that the coroutine wrapper is only created
if bdrv_nb_sectors actually calls bdrv_refresh_total_sectors.

Reported-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20230407153303.391121-9-pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>