add a regression test for 8254104.

Graalunit tests are not run on a regular basis against Open JDK, so we've lost the possibility to test OSR methods compiled by JVMCI compilers. We need to write a jtreg test about that.

A quick scenario:

1. JVMCI compiler is forced to compile some OSR code;
2. installs it (not creating MethodCounters);
3. Then the enclosing method got executed by the test;
4. C2 detects a backedge in the OSR loop;
5. Test must verify that the runtime to the compiled OSR version of the code that had been installed in #2.