docs: Apply excludes like 'vendor' and 'tests' to extensions as well

For reasons not yet understood, during CI jobs for Git release tags,
the doc publishing pipeline is scanning extensions directories even
on core-only builds.

This was realized when investigating an issue with a large fixture
file in extensions/CirrusSearch/tests/ ("interwiki.php") causing
Doxygen to crash.

When reproducing the issue locally, I found that numerous node_modules,
vendor were also being scanned that didn't need to be.

Also exclude the 'cache' dir from core $IP while at it.

Bug: T317451
Change-Id: I696f1e7edeaf7bf12fbf17613cc9ee5c8dd846b0

maintenance/Doxyfile

@@ -144,6 +144,10 @@ EXCLUDE_SYMLINKS       = YES
 EXCLUDE_PATTERNS       = LocalSettings.php \
                          .svn \
                          */.git/* \
+                         */node_modules \
+                         */resources \
+                         */tests \
+                         */vendor \
                          */includes/libs/*/README.md \
                          */maintenance/*/README.md \
                          {{EXCLUDE_PATTERNS}}

maintenance/mwdocgen.php

@@ -115,12 +115,9 @@ class MWDocGen extends Maintenance {
 
 		$this->template = $IP . '/maintenance/Doxyfile';
 		$this->excludes = [
+			'cache',
 			'images',
-			'node_modules',
-			'resources',
 			'static',
-			'tests',
-			'vendor',
 		];
 		$this->excludePatterns = [];
 		if ( $this->input === '' ) {