Update Import/Export storage path

What does this MR do?

Related to #327876 (closed)

This MR:

• Updates default Import/Export storage path (the one that is used before file is stored to object storage) to no longer point to a shared NFS mount path. Import/Export is a single sidekiq process, with sidekiq job not sharing the file with anything else. There is no need for it to be storing to a shared NFS mount (especially when on .com this is discouraged)
• Updates default import/export folder from gitlab_exports to import_export. Import process uses this location to temporarily store archive file during the import process. It's not used only for exports

Screenshots (strongly suggested)

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