Possible memory leak: bytes.Buffer grows unbounded in EncodeValue (upstream #322)

[xe-nvdk]

Upstream: vmihailenco#322

EncodeValue uses bytes.Buffer internally which grows via makeSlice. When called repeatedly, the buffer grows exponentially and does not release memory, visible via pprof.

Note: Our pooled byteSliceWriter with the 32KB cap in PutEncoder() may partially address this for the Marshal() path. The streaming encoder path may still be affected.