Fix pdb expression output leaking to debuggee stdoutpython/cpython

[shreyadesai20042009]

Fixes #143874

Problem

In remote or dual-terminal debugging setups, expressions evaluated at the pdb
prompt printed their results to the debuggee's stdout instead of the debugger
output stream.

Cause

In remote pdb mode, expression results were printed directly using print(),
bypassing pdb’s output redirection mechanism.

Fix

Route expression output through self.message() so results are sent through the
appropriate pdb output stream, including the socket-based remote debugger.

Tests

Added regression tests to ensure expression evaluation output is correctly routed
in remote pdb sessions.

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