This change makes StackFrame methods virtual to enable subclass
overrides and introduces BorrowedStackFrame, a wrapper that presents an
existing StackFrame with a different frame index.
This enables creating synthetic frame views or renumbering frames
without copying the underlying frame data, which is useful for frame
manipulation scenarios.
This also adds a new borrowed-info format entity to show what was the
original frame index of the borrowed frame.
Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>
