I use the built-in web server in PHPStorm. I would like to test server rewrites locally on this web server. Is the PHPStorm web server powered by Apache? If yes, where is the httpd.conf file located?
Is the PHPStorm web server powered by Apache?
No -- it's very simple custom web server (Java based (as whole IDE) AFAIK).
In any case: the built-in server supports some basic .htaccess instructions (not many of them, AFAIK) .. but mod_rewrite instructions are not one of them.