This CL introduces an AnnotationSet to unify annotation handling. Grammar
rules now accept a list of annotations (via annotations Symbol), where an
annotation is an Identifier starting with '@'. The new class AnnotationSet
can be used to restrict the allowed annotations and query presence of annotations
in the Make* functions.

Bug: v8:7793
Change-Id: Iad5435d4a94a3bea99aca76c23d2cffffe78a97f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1601142
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61334}