Allocate `byte[]` lazily for longer Smile binary data payloads (7-bit encoded)

[cowtowncoder]

(note: no reproduction yet via oss-fuzz, but expecting one)

Similar to #260, lazy allocation is also needed for 7-bit escaped case, to avoid potential for small payload being used to add big memory allocation on server side (possibly leading to OOME, but even if not, unreasonably high memory usage), possibly as part of DoS attack.