Optimize decodeNumeric in OrderedBytes

Currently, when we decode a byte array to a big decimal, there are plenty of BigDecimal operations, which result in a lot of only once used BigDecimal objects. Furthermore, the BigDecimal calculations are slow. We could boost this function by using String concatenation and point movement of BigDecimal. The JMH benchmark is uploaded to the attachment.

Also, I added a UT to test the encoding / decoding correctness of 200 random test samples.

The logic of the process is same as the Optimization of the encode function in the ticket HBASE-26566