Add global phase gate

Required prerequisites

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Describe the feature

Some of our decomposition patterns add a global phase that is not tracked in any way. Often this is not a problem, however, when if we transform a pure kernel into something that is equal up to global phase and attached a control to it, then the resulting circuit will be wrong, because this global phase will become relative phase. For this reason the decomposition pass is very conservative and won't do any transformation if there is a quake.apply instruction in the module.

The addition of a global phase gate can help us to keep track of the global phase added by some transformation, and will allow us to not have to be this conservative when doing transformations.

Start by reviewing the decomposition patterns that add an untracked global phase and the conservative handling of modules containing quake.apply. Determine how a global phase gate should track that phase and how transformations involving controlled kernels should use it. Done means the resulting circuits preserve the correct relative phase without requiring the current blanket restriction.