Address some PHP8 incompatibilities - Arcanist

Updates for PHP 8.2 compatibility - Arcanist

Update the arc-hg.py extension to work with mercurial 6.4

Remove call to PHP "utf8_decode()" in "phutil_utf8_strlen()"

Correct a PHP8 compatibility issue when running "arc diff" with no active branch

Fix a PHP 8.1 repository marker issue in Mercurial

Straggling fixes for PhutilURI under PHP 8.1

Add "pht_list()", a translation wrapper for lists of items

Return STDIN, STDOUT, and STDERR file descriptors from parent process

Add an ArgumentParser helper for integers

Fix more PHP 8.1 "strlen(null)" callsites in PhutilURI

Mostly remove "STDERR" and "STDOUT" constants from Arcanist

Catch more product names in "pht()", and replace newly matched Arcanist product names

Remove all product name literals in "pht()" in Arcanist

Add a "product name literal in pht()" linter