encoding/binary: Uvarint and ReadUvarint are no longer consistent

[dsnet]

Ever since ReadUvarint was modified in #41185 to limit reading to only 10 bytes, this made it such that Uvarint and ReadUvarint disagree about the definition of a varint. We should put the 10-byte limit in Uvarint as well and treat it as an overflow condition. This can occur for denormalized varints where a small integer uses more bytes to encode than necessary.

For comparison, protowire.ConsumeVarint holds to the stricter definition of a varint where it only handles up to 10 bytes and then treats any additional bytes as an overflow condition.

[ulikunitz]

Uvarint in 1.18.5 handles MaxVarintLen64=10. Do you have an example showing different behavior of ReadUvarint and Uvarint?

[dsnet]

Ah my mistake. I must have been reading an older version of the code. I see the check there.