Consolidate Shared UX Code Editor Package and Kibana React Code Editor Plugin

[rshen91]

I'm opening this issue to track consolidation of the Code Editor package and plugin. Currently the @elastic/appex-sharedux is responsible for the Code Editor within the kibana react plugin (src/plugins/kibana_react/public/code_editor) and the shared ux package code editor (packages/shared-ux/code_editor).

This is unnecessary overhead and we can be consolidated. In PR #148550 I migrated the existing code from the kibana react plugin into the shared ux package. From what I recall, we will eventually be removing the kibana react plugin. Due to time constraints at the time, I hadn't migrated existing usages of the Code Editor from Kibana and then deprecate the code editor within kibana react.

@Dosant had a great idea of having the package code be within the plugin code for the code editor. He has recently added grok language support to the kibana react code editor in this PR #155506.

List of PRs that might need to be ported to the package (needs additional review if there is more):

• Changing where CodeEditor fields get useDarkMode value #159638
• Support Grok syntax highlighting in CodeEditor #155506

Next steps:

• Move the grok language support to the Shared UX Code Editor Package
• AFAIK we should be able to follow @Dosant's idea to replace the code within the plugin with the package shared ux code editor code. I'm adding the discuss label here if @clintandrewhall might know if this won't work, please let us know thank you! This will eliminate maintenance of the kibana react code editor code since it will be imported from the package.
• Add deprecation comments to the kibana react Code Editor to avoid new users of the kibana react Code Editor

[Dosant]

Here is another pr that changes code editor #159638

[clintandrewhall]

We need to get this done relatively quickly. The two code editors are starting to diverge... we need to sync any fixes from kibana_react, dump the code editor from that plugin, and export the package version.

[Dosant]

The only notable change that the package received is the height prop here: #163211
Here are the changes for the kibana_react editor:

• [Painless lab] Improve contrast ratio between text and background color #169705