refactor: always use crypto identities to work with keys and addresses

[faustbrian]

Proposed changes

Always use identities instead of the underlying crypto.get* methods. Will make the crypto.get* methods private/protected in another bigger PR that is coming the next days.

Types of changes

• Refactoring (improve a current implementation without adding a new feature or fixing a bug)

Checklist

• I have read the CONTRIBUTING documentation
• Lint and unit tests pass locally with my changes

[ghost]

The ci/circleci: test-node11-integration-0 job is failing as of 7a8df7ddf8b092289afdd7acc08e8a76a7c21ace. Please review the logs for more information.

Once you've pushed the fixes, the build will automatically re-run. Thanks!

[codecov-io]

Codecov Report

Merging #2443 into 2.4 will decrease coverage by 0.02%.
The diff coverage is 89.28%.

@@            Coverage Diff             @@
##              2.4    #2443      +/-   ##
==========================================
- Coverage   68.26%   68.23%   -0.03%     
==========================================
  Files         387      387              
  Lines        8470     8466       -4     
  Branches      394      434      +40     
==========================================
- Hits         5782     5777       -5     
+ Misses       2640     2639       -1     
- Partials       48       50       +2

Impacted Files	Coverage Δ
packages/core/src/commands/config/forger/bip38.ts	0% <0%> (ø)	⬆️
packages/core-json-rpc/src/server/utils.ts	100% <100%> (ø)	⬆️
...ages/core-transactions/src/handlers/transaction.ts	75.86% <100%> (-0.81%)	⬇️
packages/crypto/src/crypto/message.ts	100% <100%> (ø)	⬆️
...ges/core-tester-cli/src/commands/debug/identity.ts	100% <100%> (ø)	⬆️
packages/crypto/src/crypto/bip38.ts	100% <100%> (ø)	⬆️
...sactions/builders/transactions/second-signature.ts	100% <100%> (ø)	⬆️
.../transactions/builders/transactions/transaction.ts	100% <100%> (ø)	⬆️
packages/core-forger/src/delegate.ts	100% <100%> (ø)	⬆️
packages/core-json-rpc/src/server/modules.ts	96.72% <100%> (ø)	⬆️
... and 8 more

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