staging: Migrate remaining static services to elastic workers

1. Creating venvs/docker images for remaining services:

• infra/swh-apps!7: swh.loader.mercurial
• swh.loader.cvs
• swh.loader.svn
• swh.vault.cookers
• swh.deposit.checkers
• swh.indexer journal client

2. Reference service in staging charts:

• infra/swh-charts!13: mercurial
• loader-cvs
• loader-svn
• loader-archive
• loader-cran
• loader-debian
• loader-deposit
• loader-nixguix
• loader-opam
• remaining (staging) listers
• #4540 (closed): vault cooker
• #4540 (closed): deposit checker
• swh indexer journal client

3. Decomission loader in staging static workers:

• loader-archive
• loader-cran
• loader-cvs
• loader-debian
• loader-deposit
• loader-svn
• loader-git
• loader-bzr
• loader-highpriority
• loader-maven
• loader-mercurial
• loader-npm
• loader-nixguix
• loader-opam
• loader-pypi
• remaining staging listers
• vault cookers
• deposit checker
• low hanging fruit indexers: swh indexer journal client
• migrate remaining fossology license indexer

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Migrated from T4540 (view on Phabricator)