Update dynamic circuits docs

[javabster]

new dynamic circuits are coming 2nd June, we should update the docs accordingly.

This new version will allow users to run dynamic circuits at utility scale and comes with improvements in speed, quality, and usability, including:

• Taking advantage of the Gen3 Engine stack that gives a 75x speedup in execution
• Parallel execution of branches reduces circuit duration and improves result quality
• Improvement in mid circuit measurement
• Better integration with dynamical decoupling
• More visibility in circuit timing information

These improvements will gradually roll out throughout the year, we should sync with @jyu00 for what docs need to publish when

I think they have already deprecated the following (check with jessie):

• The while, for, and switch control flow constructs
• The ability to use control flow instructions inside the body of a branch (i.e. nested control flow)
• Conditional measurements
  End of support for these deprecated instructions will be on or around 2 June 2025.

[jyu00]

I think they have already deprecated the following (check with jessie):

Yes, I opened #2708 for marking them as deprecated in the docs.