string.format extension should output scientific notation consistent with CEL spec

[zeitgeist87]

Describe the bug
The string.format extension currently outputs scientific notation rendered using a unicode multiplication sign × and superscript for the exponent 2.718280 × 10⁰⁰.

To Reproduce
Check which components this affects:

• parser
• checker
• interpreter
• string.format extension

Sample expression and input that reproduces the issue:

"%e".format([2.71828])

Test setup:
Existing test case.

Expected behavior
The output should instead be conforming to the CEL spec: 2.718280E+00 or 2.718280e+00

FLOAT_LIT      ::= -? DIGIT* . DIGIT+ EXPONENT? | -? DIGIT+ EXPONENT
DIGIT          ::= [0-9]
HEXDIGIT       ::= [0-9abcdefABCDEF]
EXPONENT       ::= [eE] [+-]? DIGIT+

[TristonianJones]

It turns out there were two issues:

• One is that golang seems to introduces narrow spaces during formatting which are not part of CLDR and the ICU4C libraries: x/text/message: scientific format is incorrect golang/go#71428
• The other is that the option to enable localization of the exponent was not obvious in C++.

It appears that both issues will be addressed, but the scope of this bug will be to temporarily strip narrow spaces on exponents until Golang updates to support the same.