feat(eslint): support eslint7 and @babel/eslint-parser

[fangbinwei]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Underlying tools
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

Other information:
replace babel-eslint with @babel/eslint-parser, bump eslint to ^7.13.0
close #5734 and #5981

[fangbinwei]

It seems @vue/cli-plugin-eslint/lint.js break in test, will check later.
it can run correctly by executing vue invoke eslint manually

related to how @babel/core loadConfig
maybe related babel/babel#11975

[haoqunjiang]

@babel/core is a peer dependency of @babel/eslint-parser, we need to explicitly install it into the user project.
Implicitly depending on package hoisting may break some package managers.

[haoqunjiang]

Looks good. Now please merge from the dev branch. I just updated yarn.lock and now there's a merge conflict here.