Feature: provide in-mem implementations by default

[paullatzelsperger]

What this PR changes/adds

All in-memory implementations of various stores are now provided as default (using the @Provider annotation). This means that it is not necessary anymore to add dependencies onto :extensions:in-memory:xyzstore anymore.

Why it does that

Having all those in-memory extensions had a couple of major downsides:

• no defaults were provided
• it was easy to forget to add them to the build file
• there were lots of pretty thin in-memory:-modules

With this PR, sane defaults are provided at all times, reducing user error and erroneous build configurations.

Further notes

• all the "core" stores, such as AssetIndex, ContractDefinitionStore etc. are now provided through the new :core:defaults module, which :core:base depends on. It is therefore sufficient to add :core:base, and a default (=in-mem) impl will be registered if no other impl is found on the classpath.
• in-mem implementations for catalog-related stores was moved into :extensions:catalog:federated-catalog-cache
• in-mem implementations for identityhub store and did document store were moved into :extensions:iam:decentralized-identity:identity-did-core

Linked Issue(s)

Closes #1130

Checklist

• added appropriate tests?
• performed checkstyle check locally?
• added/updated copyright headers?
• documented public classes/methods?
• added/updated relevant documentation?
• added relevant details to the changelog? (skip with label no-changelog)
• formatted title correctly? (take a look at the CONTRIBUTING and styleguide for details)

[codecov-commenter]

Codecov Report

Merging #1223 (16f5313) into main (9436ebf) will increase coverage by 0.14%.
The diff coverage is 44.44%.

@@             Coverage Diff              @@
##               main    #1223      +/-   ##
============================================
+ Coverage     58.94%   59.08%   +0.14%     
- Complexity     2815     2818       +3     
============================================
  Files           713      706       -7     
  Lines         15634    15612      -22     
  Branches       1049     1049              
============================================
+ Hits           9215     9224       +9     
+ Misses         5996     5966      -30     
+ Partials        423      422       -1     

Impacted Files	Coverage Δ
...actdefinition/InMemoryContractDefinitionStore.java	78.57% <ø> (ø)
...tiationstore/InMemoryContractNegotiationStore.java	88.33% <ø> (ø)
...core/defaults/policystore/InMemoryPolicyStore.java	100.00% <ø> (ø)
...ector/catalog/directory/InMemoryNodeDirectory.java	60.00% <ø> (ø)
...tor/catalog/store/InMemoryFederatedCacheStore.java	100.00% <ø> (ø)
...aceconnector/iam/did/IdentityDidCoreExtension.java	67.64% <0.00%> (-4.23%)	⬇️
...or/iam/did/hub/store/InMemoryIdentityHubStore.java	84.84% <ø> (ø)
...nector/iam/did/store/InMemoryDidDocumentStore.java	68.57% <0.00%> (ø)
...connector/spi/system/injection/ProviderMethod.java	81.25% <0.00%> (-5.42%)	⬇️
...nector/core/defaults/DefaultServicesExtension.java	33.33% <33.33%> (ø)
... and 6 more

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