Units discrepancies between __init__ and get_amount

[rkingsbury]

It appears that certain units which are supported by get_amount (including "%" and "ppb") are not supported in the __init__ method. Ideally, __init__ should be able to interpret the full set of units that can be retrieved via get_amount.

>>> s=Solution({'Ca+2': '1000 ppb'})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pyEQL/solution.py", line 250, in __init__
    self.add_solute(k, v)
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pyEQL/solution.py", line 1213, in add_solute
    if ureg.Quantity(amount).dimensionality in (
       ^^^^^^^^^^^^^^^^^^^^^
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pint/facets/plain/quantity.py", line 205, in __new__
    inst = ureg.parse_expression(value)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pint/facets/plain/registry.py", line 1388, in parse_expression
    return build_eval_tree(gen).evaluate(_define_op)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pint/pint_eval.py", line 385, in evaluate
    self.right.evaluate(define_op, bin_op, un_op),
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pint/pint_eval.py", line 396, in evaluate
    return define_op(self.left)
           ^^^^^^^^^^^^^^^^^^^^
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pint/facets/plain/registry.py", line 1386, in _define_op
    return self._eval_token(s, case_sensitive=case_sensitive, **values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pint/facets/plain/registry.py", line 1295, in _eval_token
    {self.get_name(token_text, case_sensitive=case_sensitive): 1}
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ryan/mambaforge/envs/skagit2/lib/python3.12/site-packages/pint/facets/plain/registry.py", line 647, in get_name
    raise UndefinedUnitError(name_or_alias)
pint.errors.UndefinedUnitError: 'ppb' is not defined in the unit registry

>>> s=Solution({'Ca+2': '1 ppm'})
>>> s.get_amount('Ca+2', 'ppb')
<Quantity(997.0486623989358, 'microgram / liter')>
>>> s.get_amount('Ca+2', '%')
<Quantity(9.999989981941417e-05, 'dimensionless')>