Limit decimals and shorten rejected input in exception messages on 8.1.x

[MoamenEltouny]

Summary

Fixes the two findings from the security review for the 8.1.x line: $decimals had no upper bound, and exception messages repeated the rejected input in full.

Changes

• $decimals above 100 throws InvalidArgumentException in Number::format(), Number::compact(), Number::percentage(), Bytes::format(), Money::format() and Money::compact(). Very large values used to exhaust memory with an uncatchable fatal error (Number::format(1.5, PHP_INT_MAX)) or return wrong digits: with a locale, Number::format(1.5, 100000000, false, 'en_US') returned "0".
• Exception messages quote at most 50 bytes of the value they reject, cut at a character boundary, through a new internal Support\Excerpt helper. This covers Bytes::parse(), Duration::between(), currency codes, invalid locales and MissingIntlExtension. A 1 MB input now gives a message under 100 bytes.
• Regression tests for the limit (including 100 and PHP_INT_MAX), short and cut messages, multibyte cutting, and the locale and missing-intl paths.
• The docs, MAINTAINING.md and a 8.1.2 - Unreleased changelog section describe the limit.

Compatibility

Decimals from 0 to 100 format exactly as before. Values above 100 used to crash or print wrong numbers, so rejecting them is a bug fix. Exception message text changed only for inputs longer than 50 bytes.