[Backport 2.x] Adding Spotless support framework #1888

[MitchellGale]

Description

Adds support for Spotless code formatter via ./gradlew spotlessApply and ./gradlew spotlessCheck. Apply applies the checks, check notifies which changes need to be applied.

Proposed checks commented out:
License header
Import order - sorts imports
Remove unused imports
Trim trailing whitespace
End with newline
Google Java format - https://github.com/google/google-java-format

Note: proposed spotless checks will be commented out until fix for each individual is merged. Lines will be uncommented as part of PRs addressing change.

Issues Resolved

#1101

Check List

• New functionality includes testing.
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented.
  • New functionality has javadoc added
  • New functionality has user manual doc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[codecov]

Codecov Report

Merging #1898 (77832ca) into 2.x (732e431) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##                2.x    #1898   +/-   ##
=========================================
  Coverage     97.41%   97.41%           
  Complexity     4642     4642           
=========================================
  Files           408      408           
  Lines         11506    11506           
  Branches        839      839           
=========================================
  Hits          11209    11209           
  Misses          290      290           
  Partials          7        7           

Flag	Coverage Δ
sql-engine	97.41% <ø> (ø)

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