perf: compress synthetic-project.json to save disk space.

[autonomousapps]

Partial resolution of #1604.

[SimonMarquis]

@autonomousapps FWIW here is a data point from our multi-module Android project:

From an clean project, running buildHealth, the total disk space usage is ~80 GiB.

~71% .json, 10% .bin, 5% .gz, 3% .jar, 3% .class, etc.

As an example, one of our largest feature module has a /build/reports/dependency-analysis at ~400MiB.

--- build/reports/dependency-analysis ------------------------------------
  146.9 MiB [#########################] /debugTest
  146.7 MiB [######################## ] /releaseTest
   49.2 MiB [########                 ] /debugMain
   49.0 MiB [########                 ] /releaseMain
    1.7 MiB [                         ]  usages-dependencies.json
    1.3 MiB [                         ]  unfiltered-advice.json
    1.3 MiB [                         ]  final-advice.json
   28.0 KiB [                         ]  declarations.json
   28.0 KiB [                         ]  bundled-traces.json
    4.0 KiB [                         ]  project-metadata.json
    4.0 KiB [                         ]  usages-annotation-processors.json
*Total disk usage: 396.1 MiB   Apparent size: 390.7 MiB   Items: 2,344

inside debugTest

--- build/reports/dependency-analysis/debugTest ------------------------
                                        /..
  120.1 MiB [#########################] /dependencies
   22.2 MiB [####                     ] /intermediates
    3.9 MiB [                         ] /graph
  716.0 KiB [                         ]  dependency-trace-report.json
    4.0 KiB [                         ]  android-score.json
*Total disk usage: 146.9 MiB   Apparent size: 145.1 MiB   Items: 821

and the largest item in dependencies is (unfortunately):

33.9 MiB [#########################]  com.android.tools.layoutlib__layoutlib__16.1.1.json

which is bundled in almost all our feature modules because we use it for screenshot testing.

Are there any other quick wins like gzipping that could be easily applied?

[autonomousapps]

There are two conceptually simple solutions to this issue.

1. gzip every output
2. centralize dependencies outputs (there's a lot of repetition)

I plan on taking the first step soon. Based on past results, I imagine this will have a significant positive impact on disk space usage.

Step 2, I've tried in the past, but ran into concurrent modification issues and parked the work. I'm sure it's doable; it's just that it needs to be prioritized.