feat: option to use custom espeak data

[thewh1teagle]

What does this PR do?

Add option to pass custom espeak-ng-data folder built from source for custom phonemes rules
by setting ESPEAK_DATA_PATH to the path of espeak-ng-data folder

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[mush42]

@thewh1teagle good job!
The only needed change is in the optispeech package. For ospeech we copy these files from optispeech package when building the package.

[thewh1teagle]

The only needed change is in the optispeech package. For ospeech we copy these files from optispeech package when building the package.

It's useful to change in both for inferencing and testing when training
by the way it will be more efficient if there will be optispeech-common package instead of copy duplicate files

[mush42]

@thewh1teagle sounds good. For now let's limit the change to optispeech package, and I'll implement the common package next weekend.