RFR: 8251850: Simplify ResourceMark constructors using delegation

[Kim Barrett]

Please review this simplification of the constructors for ResourceMark,
accomplished using delegating constructors.

Also made the constructors "explicit" and the class non-copyable.

CR:
https://bugs.openjdk.java.net/browse/JDK-8251850

Webrev:
https://cr.openjdk.java.net/~kbarrett/8251850/open.00/

Testing:
mach5 tier1