add more math functions and unit tests to python crate

[jimexist]

Which issue does this PR close?

add more math functions and unit tests to python crate.

based on #742 so review that first

Closes #.

Rationale for this change

• bind more already defined math functions
• add unit tests

What changes are included in this PR?

In [3]: from datafusion import functions as f

In [4]: dir(f)
Out[4]:
['__all__',
 '__doc__',
 '__loader__',
 '__name__',
 '__package__',
 '__spec__',
 'abs',
 'acos',
 'array',
 'ascii',
 'asin',
 'atan',
 'avg',
 'bit_length',
 'btrim',
 'ceil',
 'character_length',
 'chr',
 'col',
 'concat_ws',
 'cos',
 'count',
 'exp',
 'floor',
 'in_list',
 'initcap',
 'left',
 'lit',
 'ln',
 'log10',
 'log2',
 'lower',
 'lpad',
 'ltrim',
 'max',
 'md5',
 'min',
 'now',
 'octet_length',
 'random',
 'regexp_replace',
 'repeat',
 'replace',
 'reverse',
 'right',
 'round',
 'rpad',
 'rtrim',
 'sha224',
 'sha256',
 'sha384',
 'sha512',
 'signum',
 'sin',
 'split_part',
 'sqrt',
 'starts_with',
 'strpos',
 'substr',
 'sum',
 'tan',
 'to_hex',
 'translate',
 'trim',
 'trunc',
 'udaf',
 'udf',
 'upper']

Are there any user-facing changes?

[houqp]

really strange that the equality test is failing due to different object memory addresses but only for column 7 🤔

[alamb]

FYI @jorgecarleitao

[alamb]

Thanks @jimexist