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/classes/output/mustache_template_source_loader.php

@@ -69,7 +69,7 @@ class mustache_template_source_loader {
      * @param string $templatestr
      * @return string
      */
-    protected function strip_template_comments($templatestr) : string {
+    protected function strip_template_comments($templatestr): string {
         return preg_replace('/(?={{!)(.*)(}})/sU', '', $templatestr);
     }
 
@@ -87,7 +87,7 @@ class mustache_template_source_loader {
         string $name,
         string $themename,
         bool $includecomments = false
-    ) : string {
+    ): string {
         global $CFG;
         // Get the template source from the callback.
         $source = ($this->gettemplatesource)($component, $name, $themename);
@@ -152,7 +152,7 @@ class mustache_template_source_loader {
         array $seentemplates = [],
         array $seenstrings = [],
         string $lang = null
-    ) : array {
+    ): array {
         // Initialise the return values.
         $templates = [];
         $strings = [];
@@ -286,7 +286,7 @@ class mustache_template_source_loader {
      * @param string $source The template source
      * @return array
      */
-    protected function scan_template_source_for_dependencies(string $source) : array {
+    protected function scan_template_source_for_dependencies(string $source): array {
         $tokenizer = new Mustache_Tokenizer();
         $tokens = $tokenizer->scan($source);
         $templates = [];