EIP-7251: misc changes

[mkalinin]

Summary of changes:

• Remove set_compounding_withdrawal_credentials as it is unused
• Add FULL_EXIT_REQUEST_AMOUNT which is set to 0
• Add validator.effective_balance == MIN_ACTIVATION_BALANCE check to partial withdrawals
  This check is borrowed from the sweep checks. Although, satisfying this condition with partial withdrawal is not as critical as with the sweep, re-gaining the min activation balance sooner should be aligned with interest of stakers and network
• Slight refactor of process_execution_layer_withdraw_request
• Stricter comparison of withdrawal addresses on consolidation: use last 20 bytes instead of last 31 bytes of creds
• Use validator.effective_balance for consolidation churn to align its logic with the exit churn and with the churn limit computation which is EB based
• Abort voluntary exit processing if validator has pending partial withdrawals to align its processing with the process_execution_layer_withdraw_request flow

[ralexstokes]

I haven't gone through the changes, but the summary sounds good from a high-level

[fradamt]

Looks good to me!

[fradamt]

Suggested change

	has_sufficient_effective_balance = validator.effective_balance == MIN_ACTIVATION_BALANCE
	has_sufficient_effective_balance = validator.effective_balance >= MIN_ACTIVATION_BALANCE

[ralexstokes]

looks good! I lean towards merging (and ill make an issue for one comment l left, either I don't understand how the new partial withdrawals work or there is a bug...) and then ill make a testing pass in #3648