refactor(core-json-rpc): reduce complexity and add types

[faustbrian]

Proposed changes

Add types to core-json-rpc and reduce complexity & nesting.

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-unit job is failing as of 9e8f15d9a66934315602c4b8b8dd2b068e737fea. 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 #2422 into 2.4 will increase coverage by 0.23%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##              2.4    #2422      +/-   ##
==========================================
+ Coverage   66.34%   66.58%   +0.23%     
==========================================
  Files         398      388      -10     
  Lines        8540     8510      -30     
  Branches      396      434      +38     
==========================================
  Hits         5666     5666              
+ Misses       2828     2797      -31     
- Partials       46       47       +1

Impacted Files	Coverage Δ
...ages/core-json-rpc/src/server/services/database.ts	0% <0%> (ø)	⬆️
...s/core-json-rpc/src/server/modules/transactions.ts	0% <0%> (ø)
...ges/core-json-rpc/src/server/services/processor.ts	0% <0%> (ø)	⬆️
packages/core-json-rpc/src/server/utils.ts	0% <0%> (ø)
...ckages/core-json-rpc/src/server/modules/wallets.ts	0% <0%> (ø)
...ackages/core-json-rpc/src/server/modules/blocks.ts	0% <0%> (ø)
...kages/core-json-rpc/src/server/services/network.ts	0% <0%> (ø)	⬆️
packages/core-logger-winston/src/formatter.ts	41.66% <0%> (ø)	⬆️
... and 2 more

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