test(ledger): added blocks required for testing for all the eras except Conway

[jkawan]

1. Collected blocks for all the eras (except Conway) using epoch, hash and slot number. And also used https://cexplorer.io/
2. Have added the blocks in params_test.go file (except byron) for now but can move it around to any file as required by tests later

Closes #1025

[agaffney]

The block hex strings should go in a new block_test.go for each era rather than in an existing unrelated test file.

Requested changes were made.