Add autocorrection support to indentation_width rule

[nadeemnali]

Summary

This PR implements autocorrection for the indentation_width rule, allowing violations to be automatically fixed using the --fix option. The rule now conforms to CorrectableRule and will adjust indentation to match the configured width,
preserving the original style (tabs or spaces).

Details

• Implements correct(file:) for IndentationWidthRule
• Handles first-line indentation, whitespace-only lines, and mixed tabs/spaces
• Respects configuration flags for comments, compiler directives, and multiline strings
• Extracts helpers for clarity and maintainability

Testing

• All tests pass with zero regressions
• Manual verification confirms correct autocorrection

Closes #6497

[SwiftLintBot]

	1 Warning
⚠️	This PR may need tests.

	19 Messages
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