Functional style helper functions

[terrorfisch]

Similar to #694 and #692 we can add helper methods for "functional" style pulse template creation

def with_mappings(self, **MappingPTArgs):
    pass

def with_iteration(self, **ForLoopPTArgs):
    pass

For easier discoverability all methods start with with_.

• Add with_parallel_channels, with_repetition, with_mapping, with_iteration, with_time_reversal, with_appended
• Add specializations for optimization
• Add dedicated helper method paragraph to documentation and improve discoverability.
• [ x] ~~ Add helper methods to existing examples where applicable~~ Superseeded by Make convenience functionality more discoverable #804
• Add testing
• Rename with_constant_channels to with_parallel_channels since it will allow time dependet expressions in some cases when Add support for time dependent expressions in transformations. #704 is merged
• Add newspiece

[terrorfisch]

@BrllsRX Can use these functions in the new examples where applicable? I will do so mysolf over the examples I rework.

[BrllsRX]

@terrorfisch Almost all with_funcitons are tested in snake charge scan. No foreseeable problems yet. See details in Task 3 of that example.