BUG: Fix formatting of complex floats with exponents

[snitish]

• closes BUG: Printing of a pandas Series of complex numbers with e-notation has broken between 2.0.x and older versions and the newer 2.1.x, 2.2.x versions #60393
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.

>>> input_array=[(1.8816e-09+0j), (3.39676e-09+0j)]
>>> pd.Series(input_array)
0    1.881600e-09+0.000000e+                    00j
1    3.396760e-09+0.000000e+                    00j
dtype: complex128

The issue was due to the regex in the _trim_zeros_complex function not being able to handle +/- in the exponent. It assumes the complex number string to be of the form (-)xxx(+/)yyyj. I fixed the regex so it doesn't split on +/- if preceded by an exponent.
Post the fix:

>>> input_array=[(1.8816e-09+0j), (3.39676e-09+0j)]
>>> pd.Series(input_array)
0    1.881600e-09+0.000000e+00j
1    3.396760e-09+0.000000e+00j
dtype: complex128

[mroeschke]

Thanks for the PR. Could you also add a whatsnew note in v3.0.0.rst?

[mroeschke]

Could you make this a separate test?

[snitish]

Looks like I broke my branch. Will re-raise the PR.