Add all index types

[katarinasupe]

Description

• The Index class is immutable, requiring an immutable type for a property. This means that a tuple must be used instead of a list. Hence, the list returned from Memgraph will be converted to a tuple post initialization so it can be properly handled. From the user perspective, they can define property in the label-property index with a tuple or a list - both should work as expected. If the label property index is not composite, a simple string for the property should work as expected as well. These changes are handled in the Index and MemgraphIndex classes in models.py.
• Added the differentiation between different types of indexes (_convert_index_type procedure in memgraph.py), based on different Cypher queries used for their creation and deletion - LABEL (default, used for label and label+property index types, including composite indexes), EDGE (used for edge-type and edge-type+property), EDGE_GLOBAL (used for edge-property) and POINT (used for point index). By doing that, get_indexes, ensure_indexes, drop_indexes from the memgraph.py and drop_index and create_index procedures from the database_client.py should be working as expected (and drop_index and create_index became abstract, as the changes are Memgraph-related). The to_cypher procedure from the Index class was affected by this change as well. Since this change is Memgraph-related, to_cypher became abstract.
• Vector index is not included in these changes, as it's not included from the Memgraph perspective (SHOW INDEX INFO query).
• Added multiple tests to showcase how to create, drop, get and ensure all index types and to check that all works as expected.
• Docs are updated with examples for all index types.

Pull request type

Please delete options that are not relevant.

• Bugfix - order of indexes returned from database is irrelevant
• Feature - new index types
• Documentation content changes - TODO

Related issues

Closes #348

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

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Reviewer checklist (the reviewer checks this part)

• Core feature implementation
• Tests
• Code documentation
• Documentation on gqlalchemy/docs

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[antejavor]

LGTM, there are a few comments you can consider but mostly cosmetic in nature.