[DOCS] Minor clarifications needed on page describing how to use the Logs app

[Titch990]

There are some clarifications needed on this page: https://www.elastic.co/guide/en/kibana/master/xpack-logs-using.html.

• the search behaviour for highlighting
• the way that the log stream behaves when different time periods are selected during live streaming
• some terminology issues that need UI and docs updates (one raised as Suggestion for text change in Logs app #43753, plus I'm not a big fan of the term "minimap" for the timeline, but I'd like to discuss that with others to see what they think before changing it to simply "timeline").

[elasticmachine]

Pinging @elastic/kibana-docs

[KOTungseth]

@Titch990 could you add release labels to your issues?

[elasticmachine]

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