Fix lints and improve formatting

[bobozaur]

Adds more comprehensive formatting settings as well as tweaking clippy and rustc lints.

The smaller crates have been adjusted and their lints fixed, but bigger ones like aries-vcx or libvcx-core will be treated independently in different PRs since they are the main sources for conflicts.

The declared lints are fairly opinionated, but it's a list that I've been building and use with pretty much all of my projects. They are obviously up for discussion and modifications.

[codecov-commenter]

Codecov Report

Merging #986 (4b6c15b) into main (b722167) will increase coverage by 0.76%.
The diff coverage is 37.86%.

❗ Current head 4b6c15b differs from pull request most recent head 8f7cf87. Consider uploading reports for the commit 8f7cf87 to get more accurate results

@@            Coverage Diff             @@
##             main     #986      +/-   ##
==========================================
+ Coverage   29.27%   30.04%   +0.76%     
==========================================
  Files         417      415       -2     
  Lines       26096    26943     +847     
  Branches     5222     5229       +7     
==========================================
+ Hits         7640     8095     +455     
- Misses      16262    16651     +389     
- Partials     2194     2197       +3     

Flag	Coverage Δ
unittests-aries-vcx	30.04% <37.86%> (+0.76%)	⬆️

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/api/agent.rs	0.00% <0.00%> (ø)
agency_client/src/api/downloaded_message.rs	0.00% <0.00%> (ø)
agency_client/src/api/messaging.rs	0.00% <ø> (ø)
agency_client/src/api/onboarding.rs	0.00% <0.00%> (ø)
agency_client/src/configuration.rs	0.00% <0.00%> (ø)
agency_client/src/errors/error.rs	0.00% <ø> (ø)
agency_client/src/httpclient.rs	0.00% <0.00%> (ø)
agency_client/src/internal/messaging.rs	0.00% <0.00%> (ø)
agency_client/src/messages/a2a_message.rs	0.00% <0.00%> (ø)
... and 184 more

... and 36 files with indirect coverage changes

[Patrik-Stas]

lgtm, but left 1 comments