implement getenv and putenv in go (#1086)

* implement getenv and putenv in go

* fix typo

* apply formatting

* return a bool

* prevent ENV= from crashing

* optimization

* optimization

* split env workflows and use go_strings

* clean up unused code

* update tests

* remove useless sprintf

* see if this fixes the asan issues

* clean up comments

* check that VAR= works correctly and use actual php to validate the behavior

* move all unpinning to the end of the request

* handle the case where php is not installed

* fix copy-paste

* optimization

* use strings.cut

* fix lint

* override how env is filled

* reuse fullenv

* use corect function