New option to block all stripping of characters from the uncertainty in bracket uncertainty mode

[jagerber48]

The BIPM guide to the expression of uncertainty in measurements gives minimal guidance on the bracket uncertainty format. In section 7.2.2 three examples are given for bracket uncertainty.

(A) 100.02147 +/- 0.00035
(B) 100.02147(35)
(C) 100.02147(0.00035)

Note that I've made slight modifications to these examples.
Currently sciform provides access to a format like (A) by using bracket_unc=False and (B) by using bracket_unc=True

from sciform import Formatter, FormatOptions

sform = Formatter(FormatOptions(bracket_unc=False))
assert sform(100.02147, 0.00035) == '100.02147 +/- 0.00035'

sform = Formatter(FormatOptions(bracket_unc=True))
assert sform(100.02147, 0.00035) == '100.02147(35)'

However, there is no option in sciform to realize the formatting presented in option (C) where the entire decimal representation of the uncertainty is displayed in parentheses. The idea in this post is to include a new feature to permit this type of formatting.

Note that the bracket_unc_remove_seps does NOT provide the requested functionality. The bracket_unc_remove_seps feature controls whether decimal or thousandths separators are retained or stripped from the uncertainty in parentheses (in cases where those characters are present), but does not control the trimming of significant or non-significant digits.