Java: Replace SSA wrapper classes with shared implementation.

[aschackmull]

This migrates the Java SSA libraries to use the shared SSA wrapper classes.

Commit-by-commit review is very much encouraged.

[aschackmull]

I've left several deprecation annotations for a followup PR to avoid having to do a submodule bump here.

[Copilot]

Pull Request Overview

This PR modernizes the SSA (Static Single Assignment) API for Java CodeQL by renaming classes and methods to improve clarity and consistency. The changes deprecate old class and method names while introducing clearer alternatives.

• Renames core SSA classes (e.g., SsaVariable → SsaDefinition, SsaPhiNode → SsaPhiDefinition)
• Renames methods for consistency (e.g., getAUse() → getARead(), getCfgNode() → getControlFlowNode())
• Introduces new specialized SSA classes with clearer semantics (SsaCapturedDefinition, SsaImplicitCallDefinition, etc.)

Reviewed Changes

Copilot reviewed 53 out of 53 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
shared/ssa/codeql/ssa/Ssa.qll	Adds toString methods and renames SsaPhiDefinition class definition
java/ql/lib/semmle/code/java/dataflow/SSA.qll	Core SSA API with renamed classes and deprecated old names
java/ql/lib/semmle/code/java/dataflow/internal/BaseSSA.qll	Base SSA implementation updated with new class names
java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll	Internal SSA implementation restructuring
java/ql/test/**/*.ql	Test queries updated to use new API
java/ql/test/**/*.expected	Generated test expectations updated with new toString formats
java/ql/lib/**/*.qll	Various library files updated to use new API
java/ql/src/**/*.qll	Source queries updated to use new API
java/ql/lib/semmle/code/java/Expr.qll	Adds new VariableWrite class for SSA integration
java/ql/lib/change-notes/2025-10-07-ssa-api-updates.md	Documents the deprecation of old SSA API

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