feat: add `era` to `blocks/{blockId}` response for extrinsics (#685)

* fix: add eraInfo as a field in extrinsics response

* docs: update docs with GenericExtrinsicEra

* fix: switch eraInfo to era

* docs: update docs

* fix: refactor

* fix: lint

* fix: update mock data, and adjust unit tests

* docs: update GenericExtrinsicEra description

* Update docs/src/openapi-v1.yaml

Co-authored-by: David <[email protected]>

* docs: adjust docs

* tests(e2e): update kusama e2e test responses for /blocks

* tests(e2e): update the polkadot e2e tests for /blocks

* tests(e2e): update westend e2e responses for /blocks

* fix: space at end of file

Co-authored-by: David <[email protected]>