Change ComResult error to Result<S, ComError>

[Rantanen]

Closes #74

• [x] Change ComResult<S> to Result<S, ComError>
• [x] Introduce RawComResult<S> to the few places where we want to handle low level HRESULT codes directly.
• [x] Implement load_error when turning incoming HRESULT to ComError. This should check whether the interface SupportsErrorInfo.
• [x] Draft a proper error handling API.
  • ComError constructors
  • Ways to match on error code

[codecov-io]

Codecov Report

Merging #97 into master will increase coverage by 2.02%. The diff coverage is 75.07%.

@@            Coverage Diff             @@
##           master      #97      +/-   ##
==========================================
+ Coverage   78.63%   80.66%   +2.02%     
==========================================
  Files          57       57              
  Lines        4760     4975     +215     
==========================================
+ Hits         3743     4013     +270     
+ Misses       1017      962      -55

Impacted Files	Coverage Δ
intercom-common/src/attributes/com_impl.rs	100% <ø> (ø)	:arrow_up:
intercom-common/src/attributes/com_class.rs	100% <ø> (ø)	:arrow_up:
intercom/src/interfaces.rs	100% <ø> (+50%)	:arrow_up:
intercom-cpp/src/error_codes.hpp	100% <ø> (ø)	:arrow_up:
intercom-common/src/attributes/com_library.rs	0% <ø> (ø)	:arrow_up:
intercom/src/runtime.rs	0% <0%> (ø)	:arrow_up:
intercom-common/src/attributes/com_interface.rs	96.82% <100%> (+0.02%)	:arrow_up:
intercom-common/src/methodinfo.rs	90.77% <100%> (ø)	:arrow_up:
intercom/src/combox.rs	93.81% <100%> (+8.55%)	:arrow_up:
intercom-common/src/model/comcrate.rs	88.39% <100%> (+0.42%)	:arrow_up:
... and 21 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update fdaa8b1...a01b4ba. Read the comment docs.

[Rantanen]

Finally past 80% in test coverage now that the error bits are supported and tested on CircleCI where we get our coverage from!