Refactor analyzers and report builder helpers

[pixge]

Motivation

• Improve separation of concerns in analyzers by splitting analyze_file into focused helper methods for parsing, unit collection, metric extraction and result construction.
• Make the indirection analysis clearer by isolating function definition collection, alias resolution, call-graph construction and depth calculation.
• Simplify ReportBuilder.build by extracting per-file analysis, per-file report assembly and summary construction to helpers for readability and testability.
• Enable unit-testing of small pieces of logic by exposing internal helpers without changing external behavior.

Description

• Added helper methods to BpsAnalyzer (_parse_file, _collect_units, _collect_bps, _build_results) and rewrote analyze_file to use them.
• Added helper methods to CsaAnalyzer (_parse_file, _collect_module_symbols, _collect_unit_nodes, _extract_external_symbols, _build_results) and rewrote analyze_file accordingly.
• Added helper methods to IndirectionAnalyzer (_parse_file, _collect_function_definitions, _collect_aliases, _collect_call_graph, _calculate_indirection_depths) and refactored analyze_file to use them.
• Refactored ReportBuilder to extract _collect_file_analysis, _build_file_report and _build_summary, added result type imports, and added tests/test_analyzers.py with helper-focused tests.

Testing

• Ran the test suite with python -m unittest discover -s tests which executed the tests and reported Ran 12 tests with an OK result.
• Also executed python -m unittest and python -m unittest discover during development; discovery run produced no tests outside the tests directory and did not fail.
• The new tests/test_analyzers.py file contains unit tests that exercise the new helper methods for BPS, CSA, indirection and report-builder helpers and passed under the test discovery run.
• No automated tests failed as part of these runs.

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Codex Task