runtime(java): Recognise all available standard doclet tags

* Complement the tag set with @spec, {@systemProperty},
  {@summary}, @provides, @uses, @hidden, and {@index}.
* Do not hoard all tags under a single highlighting group.
* Skip over nested balanced braces in inline tags.
* Observe that tag names are case sensitive: both {@docRoot}
  and {@inheritDoc} are valid, whereas {@inheritdoc} and
  {@docroot} are not.
* In the @see tag arguments, allow for:
  - module name prefixes (e.g. java.base/java.lang.String);
  - references to arbitrary URI fragments (e.g. ##foo);
  - matching any tag variation arguments on the next line.
* Test directives and tags for Java module declarations.
* Enforce the word end for "module-info" candidates.

References:
https://bugs.openjdk.org/browse/JDK-8226279 (@spec)
https://bugs.openjdk.org/browse/JDK-8214559 ({@systemProperty})
https://bugs.openjdk.org/browse/JDK-8173425 ({@summary})
https://bugs.openjdk.org/browse/JDK-8160196 (@provides & @uses)
https://bugs.openjdk.org/browse/JDK-8073100 (@hidden)
https://bugs.openjdk.org/browse/JDK-8044243 ({@index})
https://docs.oracle.com/en/java/javase/21/docs/specs/javadoc/doc-comment-spec.html
https://github.com/openjdk/jdk/blob/jdk-21-ga/src/jdk.compiler/share/classes/com/sun/source/doctree/DocTree.java

closes: #15652

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/testdir/input/setup/java_module_info.vim

@@ -0,0 +1,30 @@
+vim9script
+
+# Test filenames are required to begin with the filetype name prefix,
+# whereas the name of a Java module declaration must be "module-info".
+const name_a: string = 'input/java_module_info.java'
+const name_b: string = 'input/module-info.java'
+
+def ChangeFilename()
+    exec 'saveas! ' .. name_b
+enddef
+
+def RestoreFilename()
+    exec 'saveas! ' .. name_a
+    delete(name_b)
+enddef
+
+autocmd_add([{
+    replace:	true,
+    group:	'java_syntax_tests',
+    event:	'BufEnter',
+    pattern:	name_a,
+    cmd:	'ChangeFilename()',
+    once:	true,
+}, {
+    group:	'java_syntax_tests',
+    event:	['BufLeave', 'ExitPre'],
+    pattern:	name_b,
+    cmd:	'RestoreFilename()',
+    once:	true,
+}])