review: add test

This test cannot pass until more work is done to translate `shared`
types in Wasmtime.

Author: abrown

tests/misc_testsuite/shared-everything-threads/builtins.wast

@@ -0,0 +1,8 @@
+;;! shared_everything_threads = true
+;;! reference_types = true
+(component
+  (core type $start (shared (func (param $context i32))))
+  (core module $libc (table (export "start-table") shared 1 (ref null (shared func))))
+  (core instance $libc (instantiate $libc))
+  (core func $spawn_indirect (canon thread.spawn_indirect $start (table $libc "start-table")))
+)