repo-updater: allow filter debug dumper by name

Created by: unknwon

As of now, the debug dump of repo perms syncing queue is coupled with the repo syncing dump that often crashes the browser tab in a production instance (with >10k repositories).

This PR adds a filter (through URL query parameter dumper) to the debug dump endpoint to be able to only dump repo perms syncing queue.

Test plan

Manually tested:

1. Add the following lines to your sg.config.overwrite.yaml:

commands:
  repo-updater:
    env:
      SRC_PROF_HTTP: ':6060'

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Related issue https://github.com/sourcegraph/customer/issues/993