Replace trait objects in libvcx_core with generics/concrete types

[bobozaur]

Replaces as much as possible the usage of Arc and trait objects to use generics/concrete types instead. This will further aid in the refactor of the primitives interface traits.
This PR also removes the feature flags for conditional anoncreds implementations in libvcx_core and node JS wrapper, relying entirely on credx.

[codecov-commenter]

Codecov Report

Merging #1011 (27b4fe7) into main (59938d7) will decrease coverage by 0.03%.
The diff coverage is 0.00%.

❗ Current head 27b4fe7 differs from pull request most recent head 39d24a5. Consider uploading reports for the commit 39d24a5 to get more accurate results

@@            Coverage Diff             @@
##             main    #1011      +/-   ##
==========================================
- Coverage   30.51%   30.48%   -0.03%     
==========================================
  Files         420      419       -1     
  Lines       26024    25967      -57     
  Branches     5025     5015      -10     
==========================================
- Hits         7942     7917      -25     
+ Misses      15893    15869      -24     
+ Partials     2189     2181       -8     

Flag	Coverage Δ
unittests-aries-vcx	30.48% <0.00%> (-0.03%)	⬇️

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

Files	Coverage Δ
...vcx/src/common/primitives/credential_definition.rs	58.95% <ø> (+0.51%)	⬆️
...ies_vcx/src/common/primitives/credential_schema.rs	19.64% <ø> (+0.34%)	⬆️
aries_vcx/src/handlers/issuance/holder.rs	42.48% <ø> (+0.54%)	⬆️
...vcx/src/protocols/issuance/holder/state_machine.rs	40.21% <ø> (+0.21%)	⬆️
aries_vcx_core/src/ledger/base_ledger.rs	0.00% <ø> (ø)
aries_vcx_core/src/wallet/agency_client_wallet.rs	0.00% <ø> (ø)
aries_vcx_core/src/wallet/base_wallet.rs	42.85% <0.00%> (-14.29%)	⬇️

... and 3 files with indirect coverage changes