[Logs UI] Add expandable rows to show example logs for categories

[katrin-freihofner]

We decided that we want to show a few example log messages for each category on the new categories screen in the logs UI.

Figma link: https://www.figma.com/file/T08kdh6YQcVCx1tzljqNHF/Logs-ML-Integration

Therefore, the table has to be transformed to hold expandable rows (each row holding one category). Expanding these rows reveals 5? example log messages, their timestamp and dataset.

There is also a single action within this expandable row Analyze in ML which links to that category in Machine learning.

#42776 is a prerequisite for this issue.

[elasticmachine]

Pinging @elastic/logs-metrics-ui (Team:logs-metrics-ui)

[mukeshelastic]

@weltenwort and I discussed about the intricacies around showing log examples for a category represented by multiple datesets and concluded the following:

• Given that log examples for a given category are represented by multiple datasets,
  When user expands the category to see the log lines
  Then she sees the anomaly score and analyze in ML link per dataset and clicking on analyze in ML link opens up single metric viewer page in ML so that users can view the anomaly score variation across time series.