runtime(java): Recognise text blocks (#14128)

Also, accept as valid the space escape sequence `\s`.

Also, consistently use the claimed `javaDebug` prefix for
syntax group definitions kept under `g:java_highlight_debug`.

Since `javaStringError` is commented out for its generality,
let's comment out `javaDebugStringError`, its copy, as well.

References:
https://openjdk.org/jeps/378
https://docs.oracle.com/javase/specs/jls/se17/html/jls-3.html#jls-3.10.7

Closes #10910.

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

runtime/syntax/testdir/input/java_escapes.java

@@ -11,13 +11,13 @@ class EscapesTests
 
 	static {
 		char ee[] = {
-			'\b', '\t',
+			'\b', '\s', '\t',
 			'\n', '\f', '\r',
 			'\"', '\'', '\\',
 		};
 
 		System.out.println(new String[] {
-			"\b", "\t",
+			"\b", "\s", "\t",
 			"\n", "\f", "\r",
 			"\"", "\'", "\\",
 		});