[WIP] Remove condition/c_if, duration, and unit from instructions

[mtreinish]

Summary

This commit removes the per instruction attributes for condition, duration, and unit. These attributes were deprecated in 1.3.0. Besides the label these attributes were the only mutable state for singleton instructions and removing them simplifies what needs to be tracked for instructions in both Python and rust. The associated methods and classes that were previously dependent on these attributes are also removed as they no longer serve a purpose. The removal of condition in particular removes a lot of logic from Qiskit especially from the transpiler because it was a something that needed to be checked outside of the normal data model for every operation.

This PR simplifies the representation of this extra mutable state in Rust by removing the ExtraInstructionAttributes struct and replacing it with a Option<Box<String>>. The Option<Box<String>> is used instead of the simpler Option<String> because this this reduces the size of the label field from 24 bytes for Option<String> to 8 bytes for Option<Box<String>> with an extra layer of pointer indirection and a second heap allocation. This will have runtime overhead when labels are set, but because the vast majority of operations don't set labels the tradeoff for optimizing for the None case makes more sense. Another option would have been to use Box<str> here which is the equivalent of Box<[u8]> (where String is the equivalent to Vec<u8>) and from a runtime memory tradeoff would be a better choice for this application if labels were commonly used as labels aren't growable. But that requires 16 bytes instead of 8 and we'd be wasting an additional 8 bytes for each instruction in the circuit which isn't worth the cost.

Details and comments

TODO:

• Fix scheduling pass updates
• Remove remaining c_if usage in tests (there's >200 instances of it still)
• Fix any failing tests not caused by the above 2 (hard to see with ~300-400 failures)
• Finish writing release notes
• Do some tuning/profiling to see if we can optimize things a bit more after the removal

[nonhermitian]

Is there a replacement method for getting circuit timing if duration is removed? It is somewhat critical to have a way to determine circuit timing for a variety of reasons.