Improve indexer workers performance

We are regularly noticed about elevated load on indexer workers since we migrated to journal client.

Possible improvments:

• infra/puppet/puppet-swh-site!544: Dedicate journal client services per node
• infra/puppet/puppet-swh-site!545: Use tmpfs
• failed: infra/puppet/puppet-swh-site!546: Activate swap on local disk
• Activate swap another way

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Migrated from T4415 (view on Phabricator)