Minor cleanups/modernizations

[JPercival]

• Made locators a final element of CqlException, fixed cases where it was missing
  • Removed logic handling that case
• Removed some code along impossible code paths
• Swapped to var in a few places
• Cleaned up some straggling javax imports.

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Codecov Report

Attention: Patch coverage is 83.01887% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 63.18%. Comparing base (fe5c101) to head (dde590a).

Files	Patch %	Lines
.../preprocessor/CqlPreprocessorElmCommonVisitor.java	84.84%	2 Missing and 3 partials :warning:
.../cqframework/cql/cql2elm/CqlCompilerException.java	57.14%	3 Missing :warning:
...va/org/cqframework/cql/cql2elm/LibraryBuilder.java	85.71%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1354 +/- ## ============================================ + Coverage 63.14% 63.18% +0.03% Complexity 6127 6127 ============================================ Files 468 468 Lines 25358 25336 -22 Branches 4719 4716 -3 ============================================ - Hits 16013 16008 -5 + Misses 7184 7171 -13 + Partials 2161 2157 -4 ```

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