Add Dokka documentation to artifacts

[tripolkaandrey]

This PR adds Dokka-generated documentation as a publish artifact.

It is done by using functionality introduced in this PR in config.

Also, while updating the config, the dead code from buildSrc, like the groovy directory, was removed.

Important details

Breaking changes were introduced in the 2.11.0 version of error_prone_core leading to a compilation error. The 2.10.0 version was forced for all other Error Prone parts to resolve the issue.

[codecov]

Codecov Report

Merging #141 (faaf3b7) into master (70a52eb) will decrease coverage by 0.11%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #141      +/-   ##
============================================
- Coverage     94.73%   94.61%   -0.12%     
+ Complexity      342      341       -1     
============================================
  Files            52       52              
  Lines           892      892              
  Branches         18       18              
============================================
- Hits            845      844       -1     
  Misses           43       43              
- Partials          4        5       +1     

[tripolkaandrey]

Vulnerabilities regarding Dokka dependencies can be fixed only by adding dependency constraints in the config repository because they originated from transitive dependencies of the precompiled script dokka-for-java.

The vulnerability of error_prone_core is not relevant as this dependency is forced to 2.10.0 which uses 30.1-jre with no mentioned vulnerabilities.

[armiol]

LGTM.