Fix ACRA bug reports not containing stack trace

[Stypox]

What is it?

• Bug fix (user facing)
• Feature (user facing)
• Code base improvement (dev facing)
• Meta improvement to the project (dev facing)

Description of the changes in your PR

This PR fixes blank reports not containing the stack trace (as seen in #3930). This was caused by MultiDex.install not being called before ACRA initialization, so ACRA could not load some of its classes and failed to initialize the stack trace collector (among others). See ACRA/acra#619 and ACRA wiki.

This PR also contains two other improvements to ACRA's initialization code:

• Skip ACRA initialization if the current process ends with :acra (i.e. is created by ACRA): https://github.com/ACRA/acra/wiki/Troubleshooting-Guide#applicationoncreate
• Remove deprecated calls to set the ReportSender class in the configuration: setReportSenderFactoryClasses() is deprecated, now extensions (ReportSenderFactory is an extension) should be registered using @AutoService. This commit adds two compile-time dependencies and only fixes a deprecation, so it can be skipped if needed. See https://github.com/ACRA/acra/wiki/Custom-Extensions#by-annotation

I think this should be merged as soon as possible, as otherwise it is not possible debug APKs by giving them to people, as there would be no stack trace in case of errors.

^{It took me ages to find the root cause of this 😩}

Testing apk

This apk crashes every time a video is opened, use that to check if ACRA correctly catches the unhandled exception.
app-debug.zip

Agreement

• I carefully read the contribution guidelines and agree to them.

[TobiGr]

LGTM
Thank you!

[wb9688]

Code looks good, though I haven't tested it myself.