add macro compile tests

[robjtede]

Add compile tests using trybuild.

[codecov]

Codecov Report

Merging #133 into master will decrease coverage by 0.18%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #133      +/-   ##
==========================================
- Coverage   61.27%   61.09%   -0.19%     
==========================================
  Files          79       80       +1     
  Lines        5012     5017       +5     
==========================================
- Hits         3071     3065       -6     
- Misses       1941     1952      +11     

Impacted Files	Coverage Δ
string/src/lib.rs	80.23% <ø> (ø)
actix-macros/tests/trybuild.rs	100.00% <100.00%> (ø)
actix-rt/src/runtime.rs	71.42% <0.00%> (-7.15%)	⬇️
actix-utils/src/task.rs	68.75% <0.00%> (-6.25%)	⬇️
actix-utils/src/counter.rs	89.28% <0.00%> (-3.58%)	⬇️
actix-server/src/server.rs	60.00% <0.00%> (-2.86%)	⬇️
actix-server/src/service.rs	70.83% <0.00%> (-2.09%)	⬇️
actix-connect/src/connector.rs	49.01% <0.00%> (-1.97%)	⬇️
actix-utils/src/oneshot.rs	94.69% <0.00%> (-1.77%)	⬇️
actix-utils/src/timeout.rs	65.07% <0.00%> (-1.59%)	⬇️
... and 12 more

---

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[robjtede]

Not been having fun trying to wrangle compiletest and from what I have seen, it's output is distinctly less useful.

Feelings somewhat match this comment: dtolnay/trybuild#13 (comment)

[robjtede]

thanks to some swift changes to trybuild this PR should be ready now that windows CI failures have been addressed.

[JohnTitor]

Looks good!