Preserve filename directive for attachments

What does this MR do and why?

Preserve filename directive for attachments

Continue overriding filename directive when content-disposition is inline to avoid rendering xml.

Avoid overriding filename directive when content-disposition is attachment.

Contributes to: #409688 (closed)

How to set up and validate locally

1. Create a project
2. Commit some xml files to it
3. Try to download the raw files see that it downloads with the correct filename by clicking the download icon

4. Try requesting the raw file and see that the content disposition header has filename directive (filename=blob) e.g curl -v http://gdk.test:3000/root/raw-files-project/-/raw/main/xml_stuff.xml

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

Related to #409688 (closed)