Codegen: Add Raw::getImmediateChild and Synth::getSynthParent

[hvitved]

Extracted from #20770. Having the parent/child relation on raw elements is needed when one wants to refer to it in the definition of synthetic elements, to avoid empty or non-monotonic recursion.

DCA is uneventful.

[Copilot]

Pull Request Overview

This PR adds infrastructure for traversing parent-child relationships in the CodeQL Swift and Rust database schemas. The changes introduce helper methods to count indexed properties and get immediate children of elements.

Key Changes:

• Added getNumberOf*() methods for all indexed properties to count elements
• Added getImmediateChild() infrastructure to retrieve children by index
• Added getSynthParent() method to get parents of synthetic elements
• Updated code generation templates to produce the new helper methods

Reviewed Changes

Copilot reviewed 5 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
swift/ql/lib/codeql/swift/generated/Synth.qll	Added getSynthParent() function and blank lines before doc comments for consistency
swift/ql/lib/codeql/swift/generated/Raw.qll	Added getNumberOf*() methods for indexed properties and getImmediateChild*() functions for parent-child traversal
swift/ql/lib/codeql/swift/generated/ParentChild.qll	Replaced max(int i | i = -1 or exists(...) | i) pattern with cleaner getNumberOf*() calls
misc/codegen/templates/*.mustache	Updated templates to generate the new helper methods
swift/ql/.generated.list, rust/ql/.generated.list	Updated checksums for regenerated files

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[redsun82]

Thanks! Also, nice simplification using getNumberOf... in ParentChild.qll 👍