feat: Install gtest from conan

[codecov-io]

Codecov Report

Merging #149 (0da6d9b) into master (3df550e) will decrease coverage by 0.02%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #149      +/-   ##
==========================================
- Coverage   96.94%   96.91%   -0.03%     
==========================================
  Files          67       68       +1     
  Lines         950     1006      +56     
==========================================
+ Hits          921      975      +54     
- Misses         29       31       +2     

Impacted Files	Coverage Δ
include/hsm/details/traits.h	85.71% <0.00%> (-14.29%)	:arrow_down:
include/hsm/details/sm.h	98.64% <0.00%> (-1.36%)	:arrow_down:
include/hsm/gen/hsm.h	96.46% <0.00%> (ø)
test/performance/main.cpp	100.00% <0.00%> (ø)
test/unit/switch_tests.cpp	100.00% <0.00%> (ø)
test/unit/traits_tests.cpp	100.00% <0.00%> (ø)
test/unit/for_each_tests.cpp	100.00% <0.00%> (ø)
test/unit/stateidx_tests.cpp	100.00% <0.00%> (ø)
test/unit/index_map_tests.cpp	100.00% <0.00%> (ø)
test/unit/has_action_tests.cpp	100.00% <0.00%> (ø)
... and 30 more

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[erikzenker]

There seems to be an issue with the gtest conan package on windows: https://github.com/bincrafters/community/issues/333

[erikzenker]

I opened a new issue: https://github.com/conan-io/conan-center-index/issues/4508

[erikzenker]

Fixed by #154