[CALCITE-7082] CalciteSystemProperty saffron.properties lookup is unusual

[chrisdennis]

To concrete things up this is what I'm suggesting as a new approach for CALCITE-7082. This implementation should (although nothing is tested) make sure that each property follows a simple priority model. Highest priority setting wins along the list:

1. System property
2. saffron.properties entry in Thread.currentThread().getContextClassLoader() (TCCL) accessible resource.
3. saffron.properties entry in CalciteSystemPropery.class.getClassLoader() accessible resource.

For comparison the current implementation is either, with a TCCL set when Calcite is first loaded:

1. System property
2. saffron.properties entry in saffron.properties available via TCCL. with no TCCL set when Calcite is first loaded:
3. System property
4. saffron.properties entry in saffron.properties available via Calcite loader.

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[github-actions[bot]]

This pull request has been marked as stale due to 30 days of inactivity. It will be closed in 90 days if no further activity occurs. If you think that’s incorrect or this pull request requires a review, please simply write any comment. If closed, you can revive the PR at any time and @mention a reviewer or discuss it on the [email protected] list. Thank you for your contributions.