Part of adopting a uniform naming policy for bridge variables,
where the variable prefix matches the role directory name.

The companion appservice variables defined by this role are folded
under the role prefix as well: matrix_mautrix_androidsms_* becomes
matrix_bridge_mautrix_wsproxy_androidsms_* and matrix_mautrix_imessage_*
becomes matrix_bridge_mautrix_wsproxy_imessage_*.

matrix_mautrix_signal_wsproxy_syncproxy_connection_string becomes
matrix_bridge_mautrix_wsproxy_syncproxy_connection_string, aligning it
with the sibling matrix_bridge_mautrix_wsproxy_syncproxy_* variables.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>