[Variant] Add negative tests for reading invalid primitive variant values

[alamb]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
As @superserious-dev says in https://github.com/apache/arrow-rs/pull/7644/files#r2140494799:

The decoders are currently tested for the happy path. It could make sense(in either this PR or a follow-up) to test for cases where the file doesn't meet the spec. For example: in the case of Decimals, ensuring that the scale byte is always in the range [0, 38].

@scovich agrees adding negative tests is important

Describe the solution you'd like
Tests for:

1. Decimals that are out of range
2. Trying to decode variants where the total length is not as expected for the primitive type (e.g try to decode a primitive int32 from a 3 byte input (it should be 5 bytes)
3. ... Others

Describe alternatives you've considered

Additional context

[superserious-dev]

take

[alamb]

label_issue.py automatically added labels {'parquet'} from #7644