[ES|QL] consider rule-based syntax highlighting

[drewdaemon]

Describe the feature: ES|QL is key to company strategy. Having syntax highlighting available at least everywhere in Elastic's UIs and possibly more broadly in the open source community is a great way to promote its use and treat it as a "first class citizen."

In https://github.com/elastic/eui/discussions/8046 we began a discussion about adding support to EUI. We originally considered using our official ANTLR lexer to power syntax highlighting as we do in the ES|QL editor. However, Regex-based highlighters are very popular (see Prism and Highlight.js) and are currently used to power EUI's code highlighting (through Prism).

The ask is to build a PoC for an ES|QL regex-based highlighter. We should evaluate its maintainability.

If we're happy with it, we should consider where it can fit in at Elastic and in the broader community.

Ideas

• EUI support
• contribute upstream to Prism/HighlightJS
• Replacing the lexer-based tokenizer in the Editor (see https://microsoft.github.io/monaco-editor/monarch.html)

[elasticmachine]

Pinging @elastic/kibana-esql (Team:ESQL)

[drewdaemon]

Switching to Monarch in the editor may also resolve https://github.com/elastic/kibana/issues/197250