[C++][Parquet] Variant specification version should be set 1 to align with the variant spec rather than 0

[aihuaxu]

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

According to the Variant specification, the specification_version field must be set to 1 to indicate Variant encoding version 1. Currently, this field defaults to 0, which violates the specification. Parquet readers that strictly enforce specification version validation will fail to read files containing Variant types.

Component(s)

C++

[raulcd]

I've marked this as backport-candidate so we cherry-pick it if we do the new release candidate for 22.0.0. Thanks @aihuaxu for working on this!

[pitrou]

Issue resolved by pull request 47835
#47835