[mdatagen] README badges template uses shortnames thus pointing to a wrong GitHub label for some extensions

[RealAnna]

Component(s)

No response

What happened?

Describe the bug

Autogenerated README “Issues” badges do not work correctly for some components : i.e. extension/storage/* are using label={{ class }}/{{ shortName }} (e.g., extension/file_storage) instead of the repo-relative component label extension/storage/. This causes badges to point to empty/incorrect issue searches.

Steps to reproduce

https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/extension/storage/filestorage/README.md

What did you expect to see?

proper label https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aextension%2Fstorage%2Ffilestorage

What did you see instead?

wrong link https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aextension%2Ffilestorage

Proposed fix:
Update mdatagen README template to use the repo-relative component path for issue labels, maybe Metadata.PackageName?

Collector version

v1.50.0

Additional context

Badges in README for storage extensions (e.g., extension/storage/filestorage, others under extension/storage/*) show zero results or wrong issues.
Confuses contributors and users trying to triage or find relevant issues.

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