lint_fix: split into separate main and common modules

- Convert most logic into a common class "SoongLintFix"
- Clean up code for clarity
- Execute using /bin/bash (python uses /bin/sh by default)

This change also makes it easier to consume common code from experimental projects.

Bug: 232058525
Test: TH
Change-Id: I421a78d5ede481baeaa5e082ce4e4ba537259bc5