feat(language-server): add python variable line for robot goto

[leojuurinen-vala]

Add parsing of the variables from python files to include their line for navigation from robot.

Root Cause:
Python variables imported from .py files had hardcoded line_no=1, col_offset=0, causing go-to-definition to always jump to the beginning of the file instead of the actual variable definition line.

Solution:
Added AST-based line number extraction that parses Python source files to find the actual line numbers and column offsets where variables are defined. Support for RF >= 7.0.

[leojuurinen-vala]

@d-biehl Do you think this is something to consider? Does it seem good for you, not sure if would require any other updates else where? Been testing it and it seems to work, but this is first change I have done for a VSCode plugin, so might be missing something.