fix(parquet/encoding): respect declared RLE payload lengths

[fallintoplace]

Rationale for this change

RLE level and boolean decoders validate their declared byte length but then give the decoder every remaining byte in the page. A short declared payload can therefore consume bytes belonging to the next encoded section instead of reporting a truncated run.

What changes are included in this PR?

• Limit Data Page V1 level decoding to its four-byte-length-prefixed payload.
• Limit Data Page V2 level decoding to its explicit byte count.
• Apply the same boundary to RLE boolean values.
• Validate the Data Page V2 length against the supplied data.

Are these changes tested?

Yes. Focused tests verify that bytes after each declared RLE interval are not consumed.