RFR (XS): 8245392: Remove duplication in class redefinition and retransformation specs

[serguei.spit...@oracle.com]

Please, review a fix for:
  https://bugs.openjdk.java.net/browse/JDK-8245392


CSR draft (one CSR reviewer is needed before finalizing it):
  https://bugs.openjdk.java.net/browse/JDK-8245433

Webrev:
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/redef-spec-dedup.1/src/

Updated specs:
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/redef-spec-dedup.1/docs/api/java.instrument/java/lang/instrument/Instrumentation.html
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/redef-spec-dedup.1/docs/specs/jdwp/jdwp-protocol.html
  http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/redef-spec-dedup.1/docs/api/jdk.jdi/com/sun/jdi/VirtualMachine.html

Summary:
  The fix is to replace in Instrumentation, JDI and JDWP spec a description of class
  redefinition or retransformation restriction with a link to the supporting JVM TI
  function where it has been already documented.
  This spec refactoring should help in cases when new 'unmodifiable in redefinition' class file attributes are added.

Testing:
  Built docs and checked the link works as expected.

Thanks,
Serguei