feat: add Time, Variant, and Binary primitive types (Issue #220)

[buddywhitman]

Closes #220

What this does

Adds the three missing primitive types requested in Issue #220 through the full type chain.

Changes by layer

Layer	Change
PrimitiveType enum	Time=24, Variant=25, Binary=26
PrimitiveTdsColumn	.time_column(), .variant_column(), .binary_column() factory methods
Expression return type	PyLegendExpressionTimeReturn ABC
Column expressions	PyLegendTimeColumnExpression, PyLegendVariantColumnExpression, PyLegendBinaryColumnExpression
Language primitives	PyLegendTime (standalone); PyLegendVariant/PyLegendBinary extend PyLegendString
Cast functions	type_factory.time(), type_factory.variant(), type_factory.binary()

tds_columns_from_json correctly round-trips all three new types (type name resolved by string).

Variant/Binary as String: intentional — both serialize to strings in standard query
engines (JSON for Variant, hex for Binary). Time-arithmetic functions can follow.

Tests

pytest tests/core/language/shared/primitives/test_new_types.py -v  # 20 passed
# Existing tds_column tests: 9/9 unaffected
# flake8 --max-line-length=127: clean
# mypy --strict: clean

[linux-foundation-easycla]

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