Explore: Display duplicate row count as number

- the pips were hard to see
- make it really clear which rows are duplicates by allocating a column to show number

Explore: Logging query live preview of matches

A logging query has a selector part and a regexp. The regexp matches are highlighted when results return.
This change adds live preview to matches when modifying the regexp in a search field.

- delegate retrieval of match query to datasource
- datasource returns search expressions to be used to highlight a live preview of matches
- logs row now takes preview highlights
- logs row renders preview highlights with dotted line to distinguish from query run matches (solid line)
- fix react-highlight-words version to ensure custom chunk matcher
- custom chunk matcher can now also take incomplete regexps, eg, `(level` without inifinte looping
- perf: debounce of live preview to 500ms
- perf: only top 100 rows get the live preview
- preview is only supported with one query row (multiple rows semantic makes this tricky: regexp for row n should only filter results for query n)

only make it possible to scan for older logs if there is at least one…

Misc styling fixes to explore

Set query empty condition in render function. Also clear query transactions when no valid query is present

Explore: Logging label stats

- added filter and stats icons to log stream labels
- removed click handler from label itself
- click on stats icon calculates label value distribution across loaded logs lines
- show stats in hover
- stats have indicator which value is the current one
- showing top 5 values for the given label
- if selected value is not among top 5, it is added
- summing up remaining label value distribution as Other

Explore: Stop scanning when clear all button is clicked

Explore: return to grid layout for logs table

- better column control than flexbox
- increased gutter and row spacing

Fix prevent removing last grafana admin permissions

fixedUnit for Flow:l/min and mL/min

got stranged result with decimalSIPrefix

Misc styling fixes to explore: start page, slate code editor colors, text highlight in auto completeter suggestion