feat(typescript-estree): support 3.8 import/export type

[bradzacher]

Based on #1696

Following babel's lead here with their existing AST that's used for flow babel/babel#11171

[typescript-eslint]

Thanks for the PR, @bradzacher!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

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[codecov]

Codecov Report

Merging #1697 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1697      +/-   ##
==========================================
+ Coverage   95.17%   95.18%   +0.01%     
==========================================
  Files         148      148              
  Lines        6938     6953      +15     
  Branches     1997     2005       +8     
==========================================
+ Hits         6603     6618      +15     
  Misses        124      124              
  Partials      211      211              

Impacted Files	Coverage Δ
packages/typescript-estree/src/convert.ts	98.87% <100.00%> (+<0.01%)	⬆️
...eslint-plugin/src/rules/no-unsafe-member-access.ts	100.00% <0.00%> (ø)