RFR: 8141133: [JVMCI] crash during safepoint deopt if rethrow_exception is set.

[Gilles Duboscq]

Hi,

Please review the following change:

Webrev:
http://cr.openjdk.java.net/~gdub/webrev-8141133/
JIRA:
https://bugs.openjdk.java.net/browse/JDK-8141133

Scopes with rethrow_exception set to true need to be handled for all types of deoptimization, not just for uncommon traps.
This change moves their handling from uncommon_trap_inner to fetch_unroll_info_helper and uses exception_oop and exec_mode = Unpack_exception rather than setting a pending exception.
fetch_unroll_info_helper can now override the exec_mode by passing it through the UnrollBlock using the existing unpack_kind field.

 Gilles