[ImportVerilog] Support Delay control

[GlowingScrewdriver]

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The chipsalliance tests for delay control currently fail. For instance:

module always_tb ();
	logic a = 0;
	always #5 a = ~a;
endmodule

It should be possible to support SystemVerilog delay controls by lowering slang::ast::DelayControl to llhd::WaitOp right?

Edit: Realised that it would have to go through Moore dialect first. Not sure what to use there; is it currently doable in Moore?