Upgrade to sbt-sonatype 3.0

[xerial]

Recently uploading artifacts to sonatype is significantly slower than before. To mitigate the issue, I've released sbt-sonatype 3.0 so that we can support parallel artifact upload:
https://github.com/xerial/sbt-sonatype#uploading-artifacts-in-parallel

And also sbt-sonatype 3.0 supports idempotent release by cleaning up previously uploaded artifacts. So if CI builds for tagged revisions fail, we can restart the failed jobs from the scratch.

cc: @takezoe @Lewuathe @shimamoto

[codecov]

Codecov Report

Merging #663 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #663   +/-   ##
======================================
  Coverage    82.1%   82.1%           
======================================
  Files         240     240           
  Lines        8874    8874           
  Branches      680     680           
======================================
  Hits         7286    7286           
  Misses       1588    1588

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