php: split php.packages to php.packages and php.extensions

So now we have only packages for human interaction in php.packages and
only extensions in php.extensions. With this php.packages.exts have
been merged into the same attribute set as all the other extensions to
make it flat and nice.

The nextcloud module have been updated to reflect this change as well
as the documentation.

pkgs/development/interpreters/php/default.nix

@@ -149,14 +149,21 @@ let
   generic' = { version, sha256, self, selfWithExtensions, ... }@args:
     let
       php = generic (builtins.removeAttrs args [ "self" "selfWithExtensions" ]);
-      packages = callPackage ../../../top-level/php-packages.nix {
+
+      packages = (callPackage ../../../top-level/php-packages.nix {
         php = self;
         phpWithExtensions = selfWithExtensions;
-      };
+      }).packages;
+
+      extensions = (callPackage ../../../top-level/php-packages.nix {
+        php = self;
+        phpWithExtensions = selfWithExtensions;
+      }).extensions;
+
       buildEnv = { exts ? (_: []), extraConfig ? "" }:
         let
           getExtName = ext: lib.removePrefix "php-" (builtins.parseDrvName ext.name).name;
-          extList = exts packages;
+          extList = exts extensions;
 
           # Generate extension load configuration snippets from
           # exts. This is an attrset suitable for use with
@@ -190,7 +197,7 @@ let
             inherit version;
             nativeBuildInputs = [ makeWrapper ];
             passthru = {
-              inherit buildEnv packages;
+              inherit buildEnv packages extensions;
             };
             paths = [ php ];
             postBuild = ''
@@ -206,7 +213,7 @@ let
     in
       php.overrideAttrs (_: {
         passthru = {
-          inherit buildEnv packages;
+          inherit buildEnv packages extensions;
         };
       });
 
@@ -238,7 +245,7 @@ let
   };
 
   defaultPhpExtensions = {
-    exts = pp: with pp.exts; ([
+    exts = pp: with pp; ([
       bcmath calendar curl ctype dom exif fileinfo filter ftp gd
       gettext gmp iconv intl json ldap mbstring mysqli mysqlnd opcache
       openssl pcntl pdo pdo_mysql pdo_odbc pdo_pgsql pdo_sqlite pgsql