[das/#106] Change patterns and templates indexes to store handles only rather than handles+targets

[andre-senna]

We use 5 indexes in AtomDB. Names, incoming set, outgoing set, type templates and patterns.

All of them are hash tables mapping from handles to values. Values are different deppending on the type of the index. The former 3 indexes map handle->List[Handle] (list of handles) while the later 2 map handle->List[Tuple[Handle, [Tuple[Handle]]]] (list of tuples (handle, targets) with the handle and the targets pod the mapped links.

Mapped link targets are stored in the last two indexes for the sake of performance in the pattern matcher query algorithm.

In the scope of the integration of the cache in the query engines, this optimization is no longer required, thus we want to simplify the API and store handle->List[Handle] for ALL indexes. This is what this PR is about.

This PR changes the AtomDB to consider a mapping of Handle->List[Handle] in the templates and in the pattern indexes.

This change is coupled with changes in the meta parser and the query engines in order to keep compliance.

SIDE EFFECT CHANGE: as a side effect of these changes, ORDERED_LINKS references (as well as is_ordered() calls) have been removed.

found some issues

[angeloprobst]

Approved, although you forgot to update these type annotations in the Database dataclass:

[angeloprobst]

Also, it seems that outgoing_set could be annotated as dict[str, set[str]].
Currently it is:

    outgoing_set: dict[str, Any] = dc_field(default_factory=dict)