ART: Refactor JIT stress mode a runtime debug flag

Do not use a constexpr default compilation threshold for the JIT.
Instead use a tri-state that distinguishes non-debug, fast-debug
and slow-debug modes.

Bug: 35644369
Test: m test-art-host
Change-Id: I3f8d71126af6b7f6b6aaa7a59cf0a42e5ee3fe01
diff --git a/runtime/runtime_options.def b/runtime/runtime_options.def
index 09a200a..78a60fa 100644
--- a/runtime/runtime_options.def
+++ b/runtime/runtime_options.def
@@ -70,7 +70,7 @@
 RUNTIME_OPTIONS_KEY (bool,                EnableHSpaceCompactForOOM,      true)
 RUNTIME_OPTIONS_KEY (bool,                UseJitCompilation,              false)
 RUNTIME_OPTIONS_KEY (bool,                DumpNativeStackOnSigQuit,       true)
-RUNTIME_OPTIONS_KEY (unsigned int,        JITCompileThreshold,            jit::Jit::kDefaultCompileThreshold)
+RUNTIME_OPTIONS_KEY (unsigned int,        JITCompileThreshold)
 RUNTIME_OPTIONS_KEY (unsigned int,        JITWarmupThreshold)
 RUNTIME_OPTIONS_KEY (unsigned int,        JITOsrThreshold)
 RUNTIME_OPTIONS_KEY (unsigned int,        JITPriorityThreadWeight)