Add http api tests for gloas finalized/justified state endpoints

[pawanjay176]

Gloas finalized states differ semantically from pre-gloas.

#9092 made the required behaviour changes for the new semantics.
In line with the todo in the PR, we should add tests for this behaviour once the db and beacon_chain components reflect the change in semantics as well

[0u-Y]

Hi, I'd like to work on this once the prerequisities are ready.