[Lens] Move TSDB and LOGSDB test into separate testing groups

[markov00]

Summary

To reduce the time spent on FTR in lens group4 and group7, I've moved TSDB and LogsDB tests into separate groups so we can have a better control over their timing.

The same happened to the same tests in serverless where I split them into 2 groups (standard scenario and downgrade scenario).
This resulted in more test groups but with smaller run time, going from a 45 minutes to 2 parallel test in 20/25 minutes.

Files index.ts and config.ts are adjusted accordingly and are duplicated as is to the newly created groups.

The README was coded with the support of AI.

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)

[jbudz]

.buildkite LGTM

[dmlemeshko]

Thank you!

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: de71aa4

Failed CI Steps

• FTR Configs #136

Test Failures

• [job] [logs] FTR Configs #136 / "before all" hook in "{root}"

Metrics [docs]

✅ unchanged

History

• 💔 Build #388422 failed fbb4997

cc @markov00