Rely on ANSI null-fallthrough where possible

[deusaquilus]

Fixes #1340

Problem

Explain here the context, and why you're making that change.
What is the problem you're trying to solve?

Check the body of Option exists, forall, map, and flatMap to see if there is an instance of If, Infix, or string-concat inside (this is only done when the ConcatBehavior in FlattenOptionOperation is set to NonAnsiConcat since outside of oracle, we don't need to have explicit null checks for every string concationation.

Although I am posting the PR now, I would like to wait until Oracle can be merged in #1295

• Unit test all changes
• Update README.md if applicable
• Add [WIP] to the pull request title if it's work in progress
• Squash commits that aren't meaningful changes
• Run sbt scalariformFormat test:scalariformFormat to make sure that the source files are formatted

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