feat[FieldData]: export to ZBF

[bzhangflex]

• Adds a to_zbf() method to FieldData for exporting E fields to a ZBF file.
• Adds a from_zbf() method to FieldDataset for importing E fields from a ZBF file.
• Adds a ZBFData class for reading ZBF files

Closes #2321

[yaugenst-flex]

Nice, looks great! Only some minor comments.

[tylerflex]

Thanks @bzhangflex , this looks great! Will be super useful and a highly requested feature!

I had a few minor comments. I'm not familiar with zemax configuration so take what I say with a bit of a grain of salt.

[tomflexcompute]

Since this is a bit experimental and largely untested, there might be cases that it will not work properly. Should we add a warning when it's called? Something like "This is an experimental feature. If you run into any issues, contact us at flexcompute.com/tidy3d/technical-support/"

[bzhangflex]

Pushed quite a few changes

• Created a read_zbf() utility function

  tidy3d/tidy3d/components/data/zbf.py

  Line 8 in fe6faac

  def read_zbf(filename: str):

• Added FieldDataset.from_zbf() for creating a new FieldDataset from a zbf file
• In to_zbf(), require the user to choose the # of field samples n_x and n_y separately. Checks that they are powers of two between 2^5 and 2^13 per Zemax manual
• If freq in to_zbf() is not specified, default to the mean of the frequencies
• units is now a kwarg
• User has the option to specify pilot beam parameters. Defaults are 0
• Updated changelog
• Updated warning messages to include support url
• use emulated_run in the pytests

[tylerflex]

Looking like it's almost there! mostly minor comments

[bzhangflex]

Thanks @tylerflex!, let me know how it looks now

[tylerflex]

looks good, thanks @bzhangflex !