app_speech_utils.c: Add horses to speech engines.

[chrsmj]

Speech Engines can now have multiple horses inside that race to get you results from different backends.

UserNote: The various Speech...() dialplan applications and the SPEECH_TEXT function now support the use of carets to control the horses in your engines.
SpeechCreate(engine^horse1)
SpeechCreate(engine^horse2)
SpeechBackground(audio,,,horse1^horse2)
SPEECH_TEXT(0^horse1)
SPEECH_TEXT(0^horse2)
SpeechDestroy(engine^horse1)
SpeechDestroy(engine^horse2)

Resolves: #593

[jcolp]

I don't agree with the use of "horses" in this. From a user facing perspective it doesn't really make sense and is not intuitive.

[github-actions]

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The currently active branches are now 18, 20, 21 and master.

[chrsmj]

cherry-pick-to: none

[gtjoseph]

Yeah, I think the horse is dead.

[chrsmj]

The use of the word "engine" in software comes directly from cars. And car engines have horse power. But "power" alone is too generic. (Also considered was powertrain but that is too long.)

[seanbright]

Maybe "candidate" would be a less controversial name?

In my mind the naming is secondary to the merits of the proposed change itself. It may be best to work through that first and then circle back on the name at the end? Just my 2¢.

[chrsmj]

Patch needs more work, will convert to draft for now. Thanks y'all for the feedback!

[sangoma-oss-cla]

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