[APM] Meta: Service transaction metrics, rollups and transaction.duration.summary field everywhere

[sorenlouv]

To improve performance we aim to make the following changes:

• Use service transaction metrics instead of transaction metrics where possible
• Use transaction.duration.summary instead of transaction.duration.histogram where possible
• Use rollups everywhere

This work is captured in the following issues:

• [APM] Support Service Metrics on the inventory overview page #138527
• [APM] Enable service metrics #146734
• [APM] Service metrics on service overview page  #152693
• [APM] Automatically select right resolution for transaction metrics  #146683
• [APM] getIsUsingTransactionEvents should check for service metrics #143848

Remaining work:

• Apply rollups everywhere
• Refactor source in roll-up response: [APM] Migrate tx latency chart and group stats to rollups/service metrics #153162 (comment)

[elasticmachine]

Pinging @elastic/apm-ui (Team:APM)