Include annotations in rule AST

[ashutosh-narkar]

No description provided.

[ashutosh-narkar]

Partly solves #6280. Originally pulled from #6593.

[johanfylling]

Looks good 👍, but I think there's one issue we need to fix.

[johanfylling]

Since we're only looking at rules declared below the annotation, won't we be dropping document-scope annotations for rules that don't happen to be located below the annotation, but have an applicable path?

E.g. this policy might not be good form, but the annotation block applies to both rules data.example.p:

package example

import rego.v1

p contains {1, rego.metadata.chain()}

# METADATA
# scope: document
# title: p-rules
p contains {2, rego.metadata.chain()}