Upgrade to TypeScript 4.0

[joshdover]

Related to #70733

Microsoft has published the beta for TypeScript 4.0: https://devblogs.microsoft.com/typescript/announcing-typescript-4-0-beta/

There are a few key features we would like to leverage to help improve the developer experience of using TypeScript in an IDE:

• Incremental builds with --noEmit
• Partial editing mode at startup

The stable release is targeting August 18th and you can track the progress here: microsoft/TypeScript#38510

We should begin the process of evaluating what this upgrade will break for us and which dependencies we may need to upgrade to support TypeScript 4.0. Though this is a "major release", TypeScript does not follow semver, so this release should not have any more breaking changes than normal. In fact, we suspect less since there is no new syntax being introduced.

Steps:

• we need to update @typescript-eslint to v4. There is a bug blocking us [no-shadow] False positive for enum typescript-eslint/typescript-eslint#2360
• update @babel to v7.11 bump babel deps to support TS v4 #74495
• update typescript version Update to TS v4 #73924

@microsoft/api-extractor complains about version incompatibility, but generates the docs. update blocked by microsoft/rushstack#1975

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)