feat(core-api): allow easy retrieval of first and last block

[faustbrian]

Often times you just want the last forged block or the genesis block to check something. This adds 2 endpoints to the block resource that retrieves those from in-memory instead of hitting the database.

What kind of change does this PR introduce?

• Bugfix
• Feature
• Refactor
• Performance
• Tests
• Build
• Documentation
• Code style update
• Continuous Integration
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

Does this PR release a new version?

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the develop branch, not the master branch
• All tests are passing
• New/updated tests are included

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

[codecov-io]

Codecov Report

Merging #2641 into 2.5 will increase coverage by 0.01%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##              2.5    #2641      +/-   ##
==========================================
+ Coverage   64.74%   64.76%   +0.01%     
==========================================
  Files         367      367              
  Lines        8220     8230      +10     
  Branches      378      378              
==========================================
+ Hits         5322     5330       +8     
- Misses       2861     2863       +2     
  Partials       37       37

Impacted Files	Coverage Δ
...ckages/core-api/src/handlers/blocks/transformer.ts	100% <100%> (ø)	⬆️
packages/core-api/src/handlers/blocks/routes.ts	100% <100%> (ø)	⬆️
packages/core-api/src/handlers/blocks/schema.ts	100% <100%> (ø)	⬆️
...ackages/core-api/src/handlers/blocks/controller.ts	71.42% <66.66%> (-1.91%)	⬇️

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