Update mock CL to use Amsterdam methods

[shohamc1]

The Amsterdam spec added engine_newPayloadV5 and engine_getPayloadV6, however the mock CL still uses Osaka methods. This is because this requires the generation of a BAL from a block before we can pass it to the mock CL.

We need to add:

• a way to generate BAL for a block (BAL is only generated in parallel execution)
• switch mock_cl.go methods to Amsterdam versions
• remove this

[VBulikov]

yperbasis added Imp2 as Importance

[taratorio]

a way to generate BAL for a block (BAL is only generated in parallel execution)

• this should be generated by our block builder when you send forkChoiceUpdate with payload attributes (e.g. via executionService.AssembleBlock), so looks like there should be a task to add "bal support in block building" first