ars-cloud compatibility with aut and Java 11

[ruebot]

What does this Pull Request do?

• Exclude servlet-api from the Hadoop dependency tree.
• Add Scala version requirement to README.

How should this be tested?

• Build tests (GitHub Actions)
• @helgeho you can use this branch of Java 11 testing with ars-cloud.

I can keep this PR open as a staging ground for tweaks for ars-cloud working Java 11 and aut on the main branch.

[codecov]

Codecov Report

Merging #510 (0b9f42f) into main (8104a65) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main     #510   +/-   ##
=========================================
  Coverage     88.83%   88.83%           
  Complexity       57       57           
=========================================
  Files            43       43           
  Lines          1012     1012           
  Branches         85       85           
=========================================
  Hits            899      899           
  Misses           74       74           
  Partials         39       39           

[ianmilligan1]

All tests are green (and build locally just to kick the tires around). 👍