Infinite recursion for completions

[tamasfe]

Schemas are crawled for completions with a given depth limit. However composite schemas (e.g. allOf, anyOf) are currently not counted as child schemas and will not count towards the schema depth. Thus it is possible to cause a stack overflow by mutually referencing schemas that are all composite schemas themselves (e.g. Target in https://raw.githubusercontent.com/metalbear-co/mirrord/main/mirrord-schema.json).

The fix itself is trivial, just treat composite schemas as children. However this will change the semantics of the user-provided limit that restricts the length of the suggested dotted keys.

To handle this properly:

• We should treat the current depth as some internal hard-limit to prevent infinite recursions.
• The user-defined limit will apply after all schemas are collected, thus will not affect performance anymore but purely UX.