Allow the use of a custom Barcode Scanning Application

[ctsims]

Right now we solely use the embedded zxing library, but there are circumstances where users might want to jump out to a much more powerful version that's more appropriate for their device or use case.

The need for this would be negated by implementing #2321, but that's potentially a significantly larger scope of work compared to a fallback option for telling the barcode scanner to use the traditional zxing intent, rather than the built-in one.

This seems to me like an App setting rather than a callout specific setting, so I think the best course of action would be to make it an application preference ("Use intent callout for scanner") that is loaded in the FormEntryActivity and passed into the widget factory .

[shubham1g5]

@ShivamPokhriyal this would be good for us to prioritize on SAAS for 2.51 . Feel free to drop any questions here.