fix: upload proguard mapping

[bruno-garcia]

1. fix: proguard upload command invocation
2. fix: allow enable only proguard command (without enabling debug file upload)
3. Check command exit code and print message if failed
4. enabled R8 in our sample

[bruno-garcia]

I opened a follow up ticket for integration testing this: #2575
Maybe @vaind can help?

I tried running the script locally to add the test, but it fails to run completely with

Line |
  12 |  BeforeAll {
     |  ~~~~~~~~~
     | The term 'BeforeAll' is not recognized as a name of a cmdlet, function, script file, or executable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

Not sure what's wrong on my local dev right now