[Parquet] Incorrect Variant extension type name

[sdf-jkl]

Describe the bug, including details regarding any error messages, version, and platform.

Description

The canonical Variant extension type name is "arrow.parquet.variant", but arrow-go returns -

arrow-go/arrow/extensions/variant.go

Line 265 in 986b027

func (*VariantType) ExtensionName() string { return "parquet.variant" }

It seems historical, because Variant was implemented in arrow-go prior to apache/arrow#47456 got merged.

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This causes:

• IPC output recordbatches with Variant ext type to be not readable by other arrow implementations
• And vice versa, other implementation's recordbatches to be not readable by arrow-go

Component(s)

Parquet