sig_analog: Add Call Waiting Deluxe support.

sig_analog: Add Call Waiting Deluxe support.

Adds support for Call Waiting Deluxe options to enhance
the current call waiting feature.

As part of this change, a mechanism is also added that
allows a channel driver to queue an audio file for Dial()
to play, which is necessary for the announcement function.

ASTERISK-30373 #close

Resolves: #271

UserNote: Call Waiting Deluxe can now be enabled for FXS channels
by enabling its corresponding option.