[Thread Safety Analysis] Fix a bug of context saving in alias-analysis (#178825)
The commit b4c98fcbe1504841203e610c351a3227f36c92a4 introduces
alias-analysis and conservatively invalidates variable definitions at
function calls. For each invalidated argument, it creates and pushes a
context. So if there are multiple arguments being invalidated, there are
more than one context being pushed. However, the analysis expects one
context at the program point of a call, causing context mismatch. This
issue could lead to false negatives.
For example,
```
MyLock->Lock(); // 'MyLock' holds the lock
Lock_t *Ptr = MyLock; // 'Ptr' aliases with 'MyLock'
// Before the fix, two contexts are saved and pushed at the call below, causing context mismatch later.
escapeAliasMultiple(&Irrelevant, &Ptr);
Ptr->Unlock(); // 'Ptr' may no longer hold the lock but the analyzer missed it due to context mismatch
```
This commit fixes the issue.
---------
Co-authored-by: Marco Elver <me@marcoelver.com>
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