Refactor pyconvert rule storage and API to scoped rules with explicit ordering and update conversions

[cjdoris]

Motivation

• Simplify and make pyconvert rules more explicit by giving each rule a scope and a deterministic ordering instead of a multipriority enum, enabling clearer matching semantics and easier high-priority insertion.
• Update the existing conversion rules (numpy, ctypes, pandas, wrap, jlwrap) to the new API and ensure registration ordering is deterministic at package init.

Description

• Reworked the pyconvert rule internals: PyConvertRule now stores type, scope, func, and an order integer, and PYCONVERT_RULES is now an ordered Pair{String,PyConvertRule}[] instead of a Dict of vectors.
• Replaced the old signature pyconvert_add_rule(tname, T, func, priority) with pyconvert_add_rule(tname, T, S, func) which requires a scope S that must be a supertype of T, and added pyconvert_add_rule_high_priority for inserting higher-priority rules.
• Adjusted rule lookup and filtering logic to consider scope and to try rules in insertion order (newer rules first) via the order field, and simplified the type/typename extraction and interface markers for arrays/buffers.
• Updated all call sites to the new API across Convert, Wrap, JlWrap, NumpyDates/numpy.jl, ctypes.jl, and pandas.jl to pass explicit scopes and to register certain rules via new high-priority helpers; removed the old PyConvertPriority enum and related exports.
• Added package initialization ordering in __init__ to register high-priority and canonical rules by calling JlWrap.init_base_rule_high_priority(), Wrap.init_wrap_rules_high_priority(), Convert.init_numpy_high_priority(), and Convert.init_pyconvert_canonical().
• Added and updated tests in test/Convert.jl to assert new behavior: rule insertion ordering, correct conversion results, and an ArgumentError if a rule is registered with a type not a subtype of its scope.

Testing

• Ran the updated test/Convert.jl unit tests which exercise added and modified conversion rules and ordering, and they passed.
• Ran the package test suite via ] test for the changed modules to ensure initialization and conversion registrations succeed, and all tests passed.

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Codex Task