res_pjsip: Expanding PJSIP endpoint ID and relevant resource length to 255 characters

This commit introduces an extension to the endpoint and relevant
resource sizes for PJSIP, transitioning from its current 40-character
constraint to a more versatile 255-character capacity. This enhancement
significantly overcomes limitations related to domain qualification and
practical usage, ultimately delivering improved functionality. In
addition, it includes adjustments to accommodate the expanded realm size
within the ARI, specifically enhancing the maximum realm length.

Resolves: #345

UserNote: With this update, the PJSIP realm lengths have been extended
to support up to 255 characters.

UpgradeNote: As part of this update, the maximum allowable length
for PJSIP endpoints and relevant resources has been increased from
40 to 255 characters. To take advantage of this enhancement, it is
recommended to run the necessary procedures (e.g., Alembic) to
update your schemas.

(cherry picked from commit f89e56c178)

res/res_pjsip_authenticator_digest.c

@@ -32,9 +32,7 @@
 	<support_level>core</support_level>
  ***/
 
-/* From the auth/realm realtime column size */
-#define MAX_REALM_LENGTH 40
-static char default_realm[MAX_REALM_LENGTH + 1];
+static char default_realm[AST_SIP_AUTH_MAX_REALM_LENGTH + 1];
 
 AO2_GLOBAL_OBJ_STATIC(entity_id);