Use an intrinsic for GetImportMetaObject and generate bytecode for the
case where import.meta has been initialized already. This way the
runtime method will only be called once per module.

Bug: v8:6693
Change-Id: If661e88e6accfb1c5795e37a80582d04f6dd87dd
Reviewed-on: https://chromium-review.googlesource.com/716536Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48801}