Builder Semantics for building SequenceExpr

[weinbe58]

Now that we have the updated compiler to generate AHS we can think about new builder semantics to be able to build the full bloqade IR expressions.

The easiest option is we just keep the builder as is and build more complicated Sequences using the API that is built into the Sequence objects already and inject those compositions via the apply method of the builder.

Otherwise we need to think about semantics to denote the end of a block of instructions contained in a Sequence and allow the user to perform a slice/name operation on that block. This is non-trivial because we need to distinguish the slicing a block vs. slicing a combination of blocks.