[LifetimeSafety] Reorganize code into modular components (llvm#162474)

Restructure the C++ Lifetime Safety Analysis into modular components
with clear separation of concerns.

This PR reorganizes the C++ Lifetime Safety Analysis code by:

1. Breaking up the monolithic `LifetimeSafety.cpp` (1500+ lines) into
multiple smaller, focused files
2. Creating a dedicated `LifetimeSafety` directory with a clean
component structure
3. Introducing header files for each component with proper documentation
4. Moving existing code into the appropriate component files:
    - `Checker.h/cpp`: Core lifetime checking logic
    - `Dataflow.h`: Generic dataflow analysis framework
    - `Facts.h`: Lifetime-relevant events and fact management
    - `FactsGenerator.h/cpp`: AST traversal for fact generation
- `LiveOrigins.h/cpp`: Backward dataflow analysis for origin liveness
- `LoanPropagation.h/cpp`: Forward dataflow analysis for loan tracking
    - `Loans.h`: Loan and access path definitions
    - `Origins.h`: Origin management
    - `Reporter.h`: Interface for reporting lifetime violations
    - `Utils.h`: Common utilities for the analysis

The code functionality remains the same, but is now better organized
with clearer interfaces between components.

Author: usx95

.github/new-prs-labeler.yml

@@ -1096,8 +1096,8 @@ clang:openmp:
   - llvm/test/Transforms/OpenMP/**
 
 clang:temporal-safety:
-  - clang/include/clang/Analysis/Analyses/LifetimeSafety*
-  - clang/lib/Analysis/LifetimeSafety*
+  - clang/include/clang/Analysis/Analyses/LifetimeSafety/**
+  - clang/lib/Analysis/LifetimeSafety/**
   - clang/unittests/Analysis/LifetimeSafety*
   - clang/test/Sema/*lifetime-safety*
   - clang/test/Sema/*lifetime-analysis*

clang/include/clang/Analysis/Analyses/LifetimeSafety.h

@@ -0,0 +1,35 @@
+//===- Checker.h - C++ Lifetime Safety Analysis -*----------- C++-*-=========//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines and enforces the lifetime safety policy. It detects
+// use-after-free errors by examining loan expiration points and checking if
+// any live origins hold the expired loans.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_LIFETIMESAFETY_CHECKER_H
+#define LLVM_CLANG_ANALYSIS_ANALYSES_LIFETIMESAFETY_CHECKER_H
+
+#include "clang/Analysis/Analyses/LifetimeSafety/Facts.h"
+#include "clang/Analysis/Analyses/LifetimeSafety/LifetimeSafety.h"
+#include "clang/Analysis/Analyses/LifetimeSafety/LiveOrigins.h"
+#include "clang/Analysis/Analyses/LifetimeSafety/LoanPropagation.h"
+
+namespace clang::lifetimes::internal {
+
+/// Runs the lifetime checker, which detects use-after-free errors by
+/// examining loan expiration points and checking if any live origins hold
+/// the expired loan.
+void runLifetimeChecker(const LoanPropagationAnalysis &LoanPropagation,
+                        const LiveOriginsAnalysis &LiveOrigins,
+                        const FactManager &FactMgr, AnalysisDeclContext &ADC,
+                        LifetimeSafetyReporter *Reporter);
+
+} // namespace clang::lifetimes::internal
+
+#endif // LLVM_CLANG_ANALYSIS_ANALYSES_LIFETIMESAFETY_CHECKER_H