[Stack Monitoring] Make sure SM queries can handle both process and processes metrics across 7.x and 8.x indices

[matschaffer]

In #113149 we'll add support for procesess metrics.

In this issue we need to address how to handle process metrics coming from older kibanas into kibana 8.0 stack monitoring UI.

We're anticipating the use of runtime fields to "upgrade" process metrics to processes but it's unclear if this has been attempted anywhere in the stack yet.

[elasticmachine]

Pinging @elastic/infra-monitoring-ui (Team:Infra Monitoring UI)

[jasonrhodes]

@matschaffer I'm not 100% clear on which parts of these 2 tickets are absolutely required for 8.0 vs. things that are planned for later in order to support the eventual need for more than 1 process.

I think the idea in this ticket is to resolve how to read from old data that still references process, is that right? Can we query for both in 8.0+ and combine them in the code for now, as an option if needed?

[matschaffer]

Can we query for both in 8.0+ and combine them in the code for now

Working out a good way to query/display both is the intent of this issue.

As for what's required for 8.0, that might be a question for @Bamieh - I see #115200 is labeled 8.0.0. If we merge that and remove process from kibana in that version, we'll need this issue (as well as elastic/beats#27569) or we'll lose kibana process metrics.

[matschaffer]

Closing this for the same reasons covered in #113149 (comment)

Rel #119560
Rel #104124