fix(eslint-plugin): [no-unnec-type-assert] handle JSX attributes

[bradzacher]

Fixes #982
Fixes #1061

I never added proper handling for JSX attributes in the rule - this fixes that.

This also fixes a few things with testing TSX files

• the rule tester code (from the 2.0 changes) didn't allow you to change the filename
• there was no tsx test file
• there was weird behaviour from the tests if I didn't clean the caches between tests
  • it wasn't actually testing the tsx code for some reason.

[armano2]

filename for now has to be absolute when used with watch program (project)

[bradzacher]

do we want to put this in the RuleTester?

[armano2]

no it should not be there, it should work correctly with relative paths
see #1439

[armano2]

@bradzacher i picked up this PR as it looked that you abandoned it (3 months ago last change),

i pushed merge + all conflicts are resolved and cleanup up code a little (most of changes was outdated and already supported on master)

i left some comments ^Up to show what i changed

dismissed

[armano2]

note: all changes related to #1061 are already present on master
df410a1#diff-9c31441197b8f835651744ab117e4b6dR223-R232

[bradzacher]

Thanks, this was on my todo list. I had some commits locally, but never got around to finishing fixing it up.

[codecov]

Codecov Report

Merging #1002 into master will decrease coverage by 0.02%.
The diff coverage is 90.9%.

@@            Coverage Diff             @@
##           master    #1002      +/-   ##
==========================================
- Coverage   94.48%   94.45%   -0.03%     
==========================================
  Files         142      142              
  Lines        6079     6083       +4     
  Branches     1727     1728       +1     
==========================================
+ Hits         5744     5746       +2     
- Misses        182      183       +1     
- Partials      153      154       +1

Impacted Files	Coverage Δ
...pt-estree/src/create-program/createWatchProgram.ts	91.17% <100%> (-1.18%)	⬇️
packages/typescript-estree/src/node-utils.ts	96.98% <100%> (ø)	⬆️
packages/eslint-plugin-tslint/src/rules/config.ts	100% <100%> (ø)	⬆️
packages/typescript-estree/src/parser.ts	94.16% <100%> (+0.09%)	⬆️
...ges/typescript-estree/src/create-program/shared.ts	87.5% <80%> (+0.83%)	⬆️