Implements rudimentary support for placeholder values inside a string
with the `PlaceholdersBuffer` class. The latter helps the newly added
sum aggregation query suggestion to automatically focus on the label
so users can easily choose from the available typeahead options.
Related: #13615
In short, the underlying problem appears to be the `onChange()` handler
being triggered after handling the blur event. Since the contents have
not actually changed this forces the typeahead state to reset which
undesirably puts a stop to propagating the selected suggestion back up
to get set.
Related: #13604
These changes were originally intended to address a bug whereby a
suggestion for an already selected label value continues to appear.
However, they also appear to fix several other problems in the area:
- Wrong suggestions when using negated label matching operators
- Misaligned label value suggestion replacements
Related: #13484
- use react-highlight-words
- add highlighting (color and border) to the matching substring of the
suggested items in the typeahead
- extracted match finding from logging datasource
- created new utils/text.ts class for text-related functions
- added more types
- some syntax rules are loaded asynchronously
- when they have been received, the query field needs to re-render
- trigger re-render via bogus edit (tried other methods but could not
find any)
