Do not override / crash if baseline.prof already exists in assets/dexopt

**Describe the bug**
There was a time where AGP + Bundletool did not work correctly when appending baseline profile data into an App Bundle.

Bundletool did not yet support the legacy bundle metadata `assets.dexopt` which AGP was using. We worked around this by manually inserting our `baseline.prof` file into the `assets/dexopt` directory ourselves. Circumventing the non-existent bundletool logic and broken logic in AGP (ref: https://partnerissuetracker.corp.google.com/issues/230361284).

This has been fixed now in newer versions of Bundletool; however, we were still using our same logic to directly insert baseline profiles into `assets/dexopt/baseline.prof`. This eventually broke when we upgraded to AGP 7.2 which will automatically generate baseline profile into the new `com.android.tools.build.profiles` metadata path.

Effectively, this default baseline profile metadata has been overriding our actual baseline profiles.

**Ask**

In `BinaryArtProfilesInjector`, there should be a check to see if a `assets/dexopt/baseline.prof` file already exists and either skip or fail as a correctness issue.

In the meantime, we will be fixing our logic to insert the baseline profile into the correct spot.

**Bundletool version(s) affected**
Version: 14.0.0