MDL-74905 composer: Regenerate with php80 and requirements raised

Now that the required PHP version has been raised to php80, set
it in the composer.json file and regenerate everything, following
the instructions @ https://docs.moodle.org/dev/Composer .

The only changes, as agreed in the issue are:
- Raise min PHP version to 8.0 (from 7.4).
- Make the php-sodium extension required (was optional).
- Small behat/behat bump to 3.12.0 (from 3.11.0)

composer.json

@@ -11,7 +11,7 @@
         "friends-of-behat/mink-extension": "^2.7.2",
         "behat/mink-goutte-driver": "^2.0",
         "symfony/process": "^4.4 || ^5.0",
-        "behat/behat": "3.11.*",
+        "behat/behat": "3.12.*",
         "oleg-andreyev/mink-phpwebdriver": "^1.2.1"
     },
     "autoload-dev": {
@@ -22,7 +22,7 @@
     "minimum-stability": "dev",
     "prefer-stable": true,
     "require": {
-        "php": ">=7.4.0",
+        "php": ">=8.0.0",
         "ext-iconv": "*",
         "ext-mbstring": "*",
         "ext-curl": "*",
@@ -40,7 +40,8 @@
         "ext-intl": "*",
         "ext-json": "*",
         "ext-hash": "*",
-        "ext-fileinfo": "*"
+        "ext-fileinfo": "*",
+        "ext-sodium": "*"
     },
     "suggest": {
         "ext-mysqli": "Needed when Moodle uses MySQL or MariaDB database.",
@@ -49,7 +50,6 @@
         "ext-oci8": "Needed when Moodle uses Oracle database.",
         "ext-tokenizer": "Enabling Tokenizer PHP extension is recommended, it improves Moodle Networking functionality.",
         "ext-soap": "Enabling SOAP PHP extension is useful for web services and some plugins.",
-        "ext-sodium": "Enabling Sodium PHP extension is recommended, it is used by Moodle encryption API.",
         "ext-exif": "Enabling Exif PHP extension is recommended, it is used by Moodle to parse image meta data."
     }
 }