Set correct movableApartFromEffects flag for datacopy()

[cameel]

Discovered in #15535 (comment).

The PR replaces hard-coded side-effects with a helper that ensures they're identical with those of the DATACOPY instruction, which the builtin uses internally.

The discrepancy was introduced in a refactor (#9283) and appears to have been a mistake.

Fortunately it had no user-visible effects. The only place where the flag is used is the LoopInvariantCodeMotion optimizer step, via SideEffectsCollector::movableRelativeTo():

solidity/libyul/optimiser/Semantics.h

Lines 77 to 84 in b5b8084

	if (
	!m_sideEffects.movableApartFromEffects ||
	m_sideEffects.storage == SideEffects::Write ||
	m_sideEffects.otherState == SideEffects::Write ||
	m_sideEffects.memory == SideEffects::Write ||
	m_sideEffects.transientStorage == SideEffects::Write
	)
	return false;

Since m_sideEffects.memory == SideEffects::Write makes the condition true anyway, the value of this flag does not actually matter for this instruction.

[github-actions]

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