MDL-65292 style: Fix all function declarations white space

This has been generated running the following Sniffs, all
them part of the Moodle's CodeSniffer standard:
- PSR12.Functions.ReturnTypeDeclaration
- PSR12.Functions.NullableTypeDeclaration
- moodle.Methods.MethodDeclarationSpacing
- Squiz.Whitespace.ScopeKeywordSpacing

All them are, exclusively, about correct spacing, so the changes
are, all them, only white space changes.

Only exceptions to the above are 3 changes what were setting the
return type in a new line, and, when that happens, the closing
parenthesis (bracket) has to go to the same line than the colon.

lib/xapi/tests/local/statement_test.php

@@ -184,7 +184,7 @@ class statement_test extends advanced_testcase {
      *
      * @return  array
      */
-    public function create_provider() : array {
+    public function create_provider(): array {
         return [
             'Agent statement with no extras' => [
                 true, [], []
@@ -413,7 +413,7 @@ class statement_test extends advanced_testcase {
      *
      * @return  array
      */
-    public function invalid_gets_provider() : array {
+    public function invalid_gets_provider(): array {
         return [
             'Method get_user on empty statement' => ['get_user', true],
             'Method get_all_users on empty statement' => ['get_all_users', true],
@@ -532,7 +532,7 @@ class statement_test extends advanced_testcase {
      *
      * @return  array
      */
-    public function invalid_data_provider() : array {
+    public function invalid_data_provider(): array {
         return [
             'No actor, no verb, no object'  => [false, false, false],
             'No actor, verb, no object'     => [false, true, false],