RFR (XS) 8222297: IRT_ENTRY/IRT_LEAF etc are the same as JRT

[coleen.phillimore at oracle.com]

Summary: Replace IRT entry points with JRT.

Tested with hs tier1-3 and built zero.  And grepped from the right level 
directory this time.

open webrev at http://cr.openjdk.java.net/~coleenp/2019/8222297.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8222297

Thanks,
Coleen