Allow decompresion without uncompressedSize

Allow decompresion without uncompressedSize

Summary:
The `LZMA2` codec doesn't allow decompression without passing the uncompressed size.
Every other codec that supports streaming decompression without the uncompressed size by streaming into an IOBuf chain.
Benchmarks show that reducing the `defaultBufferLength` to 256 KiB doesn't slow down decompression of large files, but it speeds up decompression of small files (< 1000 bytes).

Reviewed By: yfeldblum

Differential Revision: D4751571

fbshipit-source-id: 39dbe6754a1ecdc2b7ba3107e9face926d4c98ca