fix(types): invalid error msg when verifying val power in genesis doc

[lklimek]

Issue being fixed or feature implemented

Genesis doc verification returns ambiguous error msg when validator power is invalid:

json: cannot unmarshal string into Go struct field genesisDocJSON.validators of type int64

What was done?

Improved error handling to include more detailed error:

cannot unmarshal string into Go struct field genesisValidatorJSON.power of type int64

Fixed unit tests to better detect various types of parsing errors. Previously, any error in provided payload would mark the test as green, while it should detect specific errors.

How Has This Been Tested?

Breaking Changes

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[shotonoff]

🚀