Fix libvcx core lints

[bobozaur]

Addresses lints in libvcx_core crate and ends the lint removal PR series, also tweaking the CI clippy jobs to fail on any error/warning returned.

Additionally, cargo check CI jobs were removed in favor of cargo clippy jobs. They both compile the targeted crates, but clippy also checks for additional lints as well as doing all that check does. Having both is redundant.

[codecov-commenter]

Codecov Report

Merging #991 (a3a4436) into main (d507cfe) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #991      +/-   ##
==========================================
- Coverage   30.02%   30.01%   -0.01%     
==========================================
  Files         415      415              
  Lines       26913    26916       +3     
  Branches     5231     5231              
==========================================
- Hits         8081     8080       -1     
- Misses      16636    16639       +3     
- Partials     2196     2197       +1     

Flag	Coverage Δ
unittests-aries-vcx	30.01% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
agency_client/src/agency_client.rs	0.00% <0.00%> (ø)
agency_client/src/lib.rs	0.00% <ø> (ø)
agency_client/src/messages/create_key.rs	0.00% <ø> (ø)
...ries_vcx_core/src/global/mockdata/mock_settings.rs	0.00% <ø> (ø)
libvdrtools/indy-wallet/src/storage/mysql/mod.rs	24.02% <ø> (ø)

... and 3 files with indirect coverage changes