[Canvas][Data source] Use a text editor input for the ES SQL data source

[ryankeairns]

Currently, the Elasticsearch SQL data source presents users with a plain textarea input to write their query. As an improvement, we could present a text editor style UI that is more familiar to developers and analysts with query writing experience.

Additionally, we could later provide syntax highlighting, validation, hints, etc., that come with the code editor. More specifically, EUI has a Code editor component that will begin using the Monaco Editor (instead of Ace) which offers such features: https://microsoft.github.io/monaco-editor/ . You can track the EUI progress here: elastic/eui#499

Long story short, once the EUI Code editor switches to using Monaco, we should use it for our ES SQL data source input.

[elasticmachine]

Pinging @elastic/kibana-canvas

[shaunmcgough]

@poffdeluxe FYI, I put this in the roadmap tracker

[cjcenizal]

This SQL editor would have value for the @elastic/es-ui team because we'd be able to use it in Console to support SQL requests.

[ryankeairns]

Reopening this one as it is specifically referring to the ES SQL input, not the expression editor.