gh-142468: pdb: Support break filename:function syntax

[cocolato]

Support break filename:function syntax

refer: #142468

Description

This PR extends pdb's break command to support the filename:function syntax.

Previously, when a colon was present in the argument, pdb assumed the format was filename:lineno. If the part after the colon wasn't an integer, it would raise a "Bad lineno" error.

This change modifies do_break to catch the ValueError when parsing the line number. If parsing fails, it attempts to resolve the argument as a function name within the specified file using find_function.

• Issue: Feature: Support filename:function syntax for pdb break command #142468

[cocolato]

If needed, I'll add more test cases later.