mesh: Fix matching for "All Proxies" group address
mesh: Fix matching for "All Proxies" group address

The bt_mesh_fixed_group_match() function is intended to match the
various well-known group addresses, however it was never updated when
Proxy support was added.

Fixes zephyr#19015

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble