feat: modifying code generation to reduce bundle size

[gvwilson]

feat: modify code generation to reduce bundle size

1. Add bin/get_size.py so that python bin/get_size.py plotly build
   reports the number of files and total size in bytes of the plotly
   directory (where generated code is put) and the build directory
   that is populated by python setup.py build.

2. Modify codegen/__init__.py and ./setup.py so that
   python setup.py --reformat=false disables reformatting.

3. Assign an empty string to the data_docs field of generated
   validators. (This has a major impact because those docs are
   duplicated many times.)

4. Alias name of base validator during import in
   codegen/validators.py.

5. Remove the long list of CSS colors from help strings for color
   properties.

6. Replace super(Parent, self) with super() in generated code.

7. Drop use of sys.version_info and TYPE_CHECKING. Removed the check
   for Python < 3.7 using sys.version_info and as a backup checking
   typing.TYPE_CHECKING; this saves a little space and also cleans
   up the code.

8. Introduce _init_provided() for BaseFigure and BasePlotlyType
   that calls a helper function _initialize_provided() to replace
   repetitions of:

_v = arg.pop("something", None)
_v = something if something is not None else _v
if _v is not None:
    self["something"] = _v

Original size (bytes): 47086264
New size (bytes): 37142340
Change: -27%