[docs] Add KQL docs for combining wildcards with special characters & keywords

[lukasolson]

A request recently came up regarding querying documents with special characters and wildcards.

For example, given the following documents:

{
   "span.name": "Elasticsearch: POST /tmp-*/_search"
}

{
   "span.name": "Elasticsearch: POST /.kibana/_search"
}

"How do I filter for documents where the stuff inside the forward slashes does not start with a dot?"

They had tried several combinations of things with the wildcard inside of quotes, which doesn't work (we should make this explicit inside the docs). The answer ultimately came down to a combination of escaping special characters and wildcards:

span.name: Elasticsearch\: POST /*/_search AND NOT Elasticsearch\: POST /.*/_search

The follow-up question then was "What if the value contained and or or?" And the answer is to also escape keywords (which I don't think we have anywhere inside our docs): /and

We should add some more detail to our docs for these two things:

1. Wildcards cannot be used inside quotes. If using wildcards, don't use quotes and escape all special characters.
2. How to escape keywords (and/or/not)

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[kertal]

Closing this because it's not planned to be resolved in the foreseeable future. It will be tracked in our Icebox and will be re-opened if our priorities change. Feel free to re-open if you think it should be melted sooner.