To improve the FreqRange class

[Frank-DingYC]

Is your feature request related to a problem? Please describe.
@George-Guryev After using the class FreqRange, I find there are several problems：

1. There is no td.FreqRange.wvl_width, which is required on the GUI.
2. When I see the td.FrequencyUtils, I suggest including the following frequency bands:
   a. LTE frequency band and 5G NR Band, which are widely used for our cellphone/smart consumer devices design.
   b. Satellite frequency and mm wave band, which are widely used for mm-wave applications.
3. It's unclear how and where we use td.FrequencyUtils.

Describe the solution you'd like
For the first problem, it's better to provide it.
For the second problem, I guess we can just simply add those bands.

Describe alternatives you've considered
For the third problem, I guess it's better to combine those frequency bands with the post-processing results. Especially for the frequency vs. amplitude chart (S-parameters, flux, Gain($\theta_0$,$\phi_0$), Radiation Efficiency...). The chart might be like:

If Flexcompute Team Member
Please assign an estimate for the "priority" of the project (tiny, small, medium, large, XL)

[yuanshen-flexcompute]

@George-Guryev-flxcmp I am attaching my feedback for the FreqRange class here as well. Nice job! I think this can turn into nice replacement for the numpy array. Some comments:

• For the spacing parameter of FreqRange.freqs(), it would be nice to provide a logarithmic spacing option (i.e. points are equally spaced in log10(f) scale).
• My understanding is that for now, we should use FreqRange.freqs() to generate frequency point lists during the simulation setup. In that case, I would also suggest adding some sort of manual_freq_point argument to that utility - the rationale being that sometimes users might want to request specific frequency point(s) that is relevant to their model. Example, something like freqs = FreqRange.freqs(401, manual_freq_points=[28e9, 30e9]) would return 401 points between f_min and f_max, but also making sure to include 28e9 and 30e9 Hz.
• This might already have been discussed, but in the long run, I think it would be good for FreqRange to replace list in all components of Tidy3D which requires a freqs input. Example, instead of currently my_tcm = TerminalComponentModeler(freqs=np.linspace(f_min, f_max, 401), ...), we can instead use my_tcm = TerminalComponentModeler(freqs=FreqRange.from_freq_interval(f_min, f_max), ...). That said, it might then be necessary to include num_points as an attribute of FreqRange instead of a parameter into the freqs() method.

Nice work!