Use pcov instead of xdebug because it is much faster

Author: PowerKiKi

.github/workflows/ci.yml

@@ -96,7 +96,7 @@ jobs:
         with:
           php-version: 7.4
           extensions: ctype, dom, gd, iconv, fileinfo, libxml, mbstring, simplexml, xml, xmlreader, xmlwriter, zip, zlib
-          coverage: xdebug
+          coverage: pcov
 
       - name: Get composer cache directory
         id: composer-cache