Improve line directive handling

[Martin521]

Description

Fixes #17529
Unblocks work on #17507
Some small clean-up in the ComponentTests project

Checklist

• Test cases added
• Performance benchmarks added in case of performance changes
• Release notes: not needed (no behavioral change)

[github-actions]

❗ Release notes required

@Martin521,

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Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/9.0.100.md	No release notes found or release notes format is not correct