Receipt of an RTP packet currently causes the formats on an PJSIP channel to
change to the format of the RTP packet. In some off-nominal cases it's possible
for this to be a format that has not been configured or negotiated. This change
makes it so only formats explicitly configured on the endpoint are allowed.

ASTERISK-25258 #close

Change-Id: If93d641fb6418a285928839300d7854cab8c1020