fix(diag): Better error messages when trying to call a non-callable type

[tibordp]

Fixes #118

The current error message when trying to call a non-callable object was pretty bad. This adds more information + adds a special case for possible field/method confusion.

[codecov]

Codecov Report

Attention: Patch coverage is 36.36364% with 7 lines in your changes missing coverage. Please review.

Project coverage is 88.60%. Comparing base (304bf3f) to head (abebb2d).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/alumina-boot/src/ir/mono/intrinsics.rs	0.00%	6 Missing ⚠️
src/alumina-boot/src/ir/mono/mod.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #119      +/-   ##
==========================================
- Coverage   88.62%   88.60%   -0.02%     
==========================================
  Files          35       35              
  Lines       17138    17144       +6     
==========================================
+ Hits        15188    15191       +3     
- Misses       1950     1953       +3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.