[lldb][ExpressionParser][NFCI] Log pointers as hex (#91989)

This ensures that we log pointers as lower-case hex. E.g., instead of:
```
 LayoutRecordType on (ASTContext*)0x000000010E78D600 'scratch ASTContext' for (RecordDecl*)0x000000010E797
```
we now log:
```
 LayoutRecordType on (ASTContext*)0x000000010e78d600 'scratch ASTContext' for (RecordDecl*)0x000000010e797
```

Which is consistent with how the AST dump gets emitted into the log.
This makes it easier to correlate pointers we log from LLDB and pointers
that are part of any AST dumps in the same `expr` log.