feature: Add delay instruction for circuits

[rmshaffer]

Issue #, if available:
#974

Description of changes:
Starting with the changes from #993 and performing the additional work required to merge to main.

The biggest outstanding items are:

• Delay (like the existing Barrier) should inherit from CompilerDirective rather than Gate, since it is an instruction that affects the compilation of a program rather than the quantum state. See this comment thread.
• Significant duplication between the new DurationGate class and the existing AngledGate class that should be reduced. See this comment thread.

Testing done:
tox

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (a76c4e2) to head (af91e62).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #1002   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          162       163    +1     
  Lines        10450     10526   +76     
  Branches      1296      1302    +6     
=========================================
+ Hits         10450     10526   +76     

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[nonhermitian]

Is there any action in this direction anymore? Not having a barrier makes benchmarking via AWS difficult because any mirror circuits collapse unless verbatim mode is used, e.g. unitaryfoundation/metriq-gym#329

[rmshaffer]

@nonhermitian we need to get barrier added as a supported instruction in the Braket service first, and then we'll merge support for the barrier instruction here. Thank you for the nudge - I'll bring this up with the product team and will follow up when we have a timeline.

[rmshaffer]

Is there any action in this direction anymore? Not having a barrier makes benchmarking via AWS difficult because any mirror circuits collapse unless verbatim mode is used, e.g. unitaryfoundation/metriq-gym#329

@nonhermitian We are picking up this work and hope to have support ready within a few weeks. Will post status updates here as we progress.