feat: update converter to use file_match block

[kalleep]

PR Description

Now that #4743 is merged we can update converters to use file_match block instead of going through local.file_match.

Which issue(s) this PR fixes

fixes: #4744

Notes to the Reviewer

PR Checklist

• CHANGELOG.md updated
• Documentation added
• Tests updated
• Config converters updated

[Copilot]

Pull Request Overview

This PR refactors the promtail converter to eliminate the intermediate local.file_match component in favor of using the built-in file_match block within loki.source.file. This simplifies the generated Alloy configuration by reducing component indirection.

• Removed the local.file_match component generation logic
• Updated code generator to include file_match block directly in loki.source.file
• Removed unused import and struct fields related to file matching

Reviewed Changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/converter/internal/promtailconvert/internal/build/scrape_builder.go	Refactored to use inline file_match block instead of separate local.file_match component; removed getExpandedFileTargetsExpr() method and added convertFileMatchConfig() helper
CHANGELOG.md	Added enhancement entry documenting the converter update
internal/converter/internal/staticconvert/testdata_linux/promtail_prom.alloy	Updated test data to reflect new pattern with inline file_match block
internal/converter/internal/staticconvert/testdata_linux/promtail_metrics.alloy	Updated test data to reflect new pattern with inline file_match block
internal/converter/internal/promtailconvert/testdata/*.alloy	Updated all test data files (26 files) to use inline file_match block and direct target references instead of local.file_match component

[ptodev]

I know it's not considered experimental, but do we need to do more dogfooding before rolling it out as a default more widely?

[kalleep]

I know it's not considered experimental, but do we need to do more dogfooding before rolling it out as a default more widely?

Sure we can target next release with this specific change if you are more comfortable with it?

[ptodev]

Targeting next release would be nice. Especially if for some reason users are translating the config on the latest version, but still expect the previous Alloy version to work with the translated config.