[eslint-parser] Represent static using a Keyword token

[nicolo-ribaudo]

Q	A
Fixed Issues?
Patch: Bug Fix?	Yes
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This matches ESLint's behavior - https://astexplorer.net/#/gist/f9cf0a5789035bf20a616f3d2ef06699/latest

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[JLHwung]

Related: I am refactoring token storage. The goal is to use number ( const enum ) as token and then we can internally categorize other keyword-like names (await, async, type, from, get, set and static) as unique keyword token type. Of course the exposed tokens will still maintain Babel 7 compatibility but we could change the tokens layout in Babel 8, which should simplify the token conversion here.