CI performance impovements

[rzadp]

The following has been done in order to improve CI performance:

• Introduced an Initialize job that initializes the project with dependencies and compiles the contracts
  • The result, saved in CI cache, is used by subsequent build, lint, test and cover jobs
• Yarn's cache is saved in CI cache to use in every Initialize run
• Compiled contracts are saved in CI cache to use in every Initialize run
  • The cache is based on a key with commit hash of the contracts, so if we update contracts submodule then the cache will be invalidated
• Saving yarn install:deploy output in a CI artifact in order to get rid of large wall of text in CI logs coming from node-gyp that does not conform to --silent switch

E2E

• The e2e sub-projects cannot make use of the Initialize job because all of the initialization, installing dependencies, compiling contracts happens in the docker build system.
• Enabling docker layer caching allows to cache built docker layers in the e2e jobs run
  • Apparently the docker layer caching performance varies, not always the layers are taken from cache. I have included slower and quicker runs in the results

Notes

• From what I've read the docker layer caching feature might become a paid feature in the future
• I didn't find any more improvements, also I don't think that we can share pulling parity, redis etc. docker images between the e2e jobs. I'd say we close Duplicated actions in the run of e2e tests on CircleCI #65 but keep eye on further opportunities for improvement

Results

Before (current master)

After, slowest run

After, quicker oracle-e2e run

After, quicker ui-e2e run