Respect inlined schemas annotations even if --schema flag isn't used

[johanfylling]

The schemas annotation supports inlined schema definitions (undocumented).

# METADATA
# scope: package
# schemas:
#   - input: {"type": "boolean"}
package main

Currently, the schemas annotation only affect type checking if the --schema flag is passed to the eval- and check commands. Considering the --schema requires you to supply a file or directory, its use is redundant and confusing when only inlined schemas are used.

Currently, annotation parsing is only triggered when the --schema flag is used, or if a rego.metadata.* function is called within the policy. Consider introducing a new flag for enabling use of inlined schemas, to make it possible to opt-out of unwanted annotation parsing.

Note: This functionality has limited use while inlined schemas remain undocumented.