Add "Compute Exact DC Point" functionality to siwave SYZ sweep

[pyAnsysUser]

Description of the feature

Computing exact DC point enables high accuracy PDN analysis through API

Steps for implementing the feature

Since causality and exact DC are mutually exclusive, I expecting enabling one disables the other. There may be an associated message with this. This may steer the implementation since I do not see if the causality option is documented as accessible though API either.

Useful links and references

ScrSIwaveSyzComputeExactDcPoint()
ScrSIwaveSyzEnforceCausality()

[hui-zhou-a]

@pyAnsysUser you can set compute_dc_point after the PR is merged.

sweep = setup1.add_frequency_sweep(
            "sweep1",
            frequency_sweep=[
                ["linear count", "0", "1kHz", 1],
                ["log scale", "1kHz", "0.1GHz", 10],
                ["linear scale", "0.1GHz", "10GHz", "0.1GHz"],
            ],
        )
sweep.compute_dc_point = True

[pyAnsysUser]

This is an excellent addition, thank you!

[pyAnsysUser]

@ring630 what is expected outcome of the line:
["linear count", "0", "1kHz", 1],
I see a linear count with two frequencies but a single output point as ambiguous- I know that this is the way it is in the documentation, but is this better than
["linear count", "0", "0", 1],
or
["linear count", "1kHz", "1kHz", 1],

[hui-zhou-a]

@pyAnsysUser it will add 0hz in the frequency list.

["linear count", "0", "0", 1] also works.