[JVMCI] failed speculations list must outlive any nmethod that refers to it

Very rarely when running Graal's unit tests, this happens:

#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (methodData.cpp:829), pid=93495, tid=93496
# fatal error: Adding to failed speculations list that appears to have been freed. Source: 3183{static void com.oracle.graal.compiler.enterprise.test.CountedStripMiningRangeCheckTest.testStridePosScalePos(jlong, jlong, jlong, jlong)}
#
# JRE version: Java(TM) SE Runtime Environment GraalVM 22.1.0-dev (17.0.1+7) (build 17.0.1+7-LTS-jvmci-21.3-b02)
# Java VM: Java HotSpot(TM) 64-Bit Server VM GraalVM 22.1.0-dev (17.0.1+7-LTS-jvmci-21.3-b02, mixed mode, sharing, tiered, jvmci, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0xb9087e] FailedSpeculation::add_failed_speculation(nmethod*, FailedSpeculation**, unsigned char*, int)+0x12e
#
# Core dump will be written. Default location: Core dumps may be processed with "/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h" (or dumping to /home/davileop/Work/Source/graal-enterprise/graal-enterprise/core.93495)
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#

This should be avoidable by allowing a HotSpotNmethod created in a unit test to hold a strong reference to the failed speculations list.