RFR: 8179460: Fix unnecessary uses of {@docRoot} in serviceability APIs

[Jonathan Gibbons]

Please review the following simple changes to update use of {@docRoot} 
in doc comments now that we have a single docs bundle.

Most instances in this review can be replaced with direct references 
using @see or {@link}. One use of {@docRoot} remains, but modified, to 
refer to an explicit anchor in another file.

JBS: https://bugs.openjdk.java.net/browse/JDK-8179460
Webrev: http://cr.openjdk.java.net/~jjg/8179460/webrev/

-- Jon