8231844: Enhance type signature characters in classfile_constants.h and improve the JVM to use type signature characters more consistently

Increase the use of type signature constants instead of hard coded characters within the JVM.

Co-authored-by: John Rose <john.r.rose@oracle.com>
Reviewed-by: coleenp, dholmes, fparain

src/java.base/share/native/include/classfile_constants.h.template

@@ -144,6 +144,10 @@ enum {
 /* Type signatures */
 
 enum {
+    JVM_SIGNATURE_SLASH         = '/',
+    JVM_SIGNATURE_DOT           = '.',
+    JVM_SIGNATURE_SPECIAL       = '<',
+    JVM_SIGNATURE_ENDSPECIAL    = '>',
     JVM_SIGNATURE_ARRAY         = '[',
     JVM_SIGNATURE_BYTE          = 'B',
     JVM_SIGNATURE_CHAR          = 'C',