Android: add javac intermediates to classpath

[damianw]

This adds the classes from build/intermediates/javac to the classpath used to compile the code, in order for the compiler to be able to resolve references to Java code (included that which is generated). This resolves issues such as #3488 among probably others.

A test is included which enables viewBinding on a sample project and verifies that the Detekt invocation doesn't produce any errors about unresolved references to the generated classes.

Downside: invoking Detekt (with type resolution) now depends on the full assembly of the variant. Before (I think?) this was not a requirement. This is a bit of a trade-off, although in practice I don't think it makes too much of a difference considering the "expensive" type resolution tasks are typically run on CI (we configure Detekt in this way already in a fairly large codebase and haven't found it to be especially burdensome). It would be possible to make this an opt-in option if needed though. 🙃

[codecov]

Codecov Report

Merging #3867 (9f78146) into main (4d4a11a) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #3867   +/-   ##
=========================================
  Coverage     83.64%   83.64%           
  Complexity     3116     3116           
=========================================
  Files           456      456           
  Lines          8966     8966           
  Branches       1747     1747           
=========================================
  Hits           7500     7500           
  Misses          552      552           
  Partials        914      914           

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[picklebento]

Thank you for the improvements. I think the long-term goal is to build detekt as a compiler plugin, but we should help improve the existing android integration at the same time.