Generate a BTI instruction at each target of an indirect branch
(BR/BLR). An indirect branch that doesn't jump to a BTI instruction
will generate an exception on a BTI-enabled core. On cores that do
not support the BTI extension, the BTI instruction is a NOP.

Targets of indirect branch instructions include, among other things,
function entrypoints, exception handlers and jump tables. Lazy deopt
exits can potentially be reached through an indirect branch when an
exception is thrown, so they also get an additional BTI instruction.

Bug: v8:10026
Change-Id: I0ebf51071f1b604f60f524096e013dfd64fcd7ff
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1967315
Commit-Queue: Georgia Kouveli <georgia.kouveli@arm.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66751}