Use lz4 instead of zstd for the DB

zstd was recommended for the base layer only, due to its CPU requirements. That
was a misreading on mhy behalf.

lz4 gets ~5% better compression than snappy with ~30% faster performance. zstd
does ~25% better than lz4 yet at ~30% of the performance.

Cargo.lock

@@ -4713,8 +4713,8 @@ dependencies = [
  "glob",
  "libc",
  "libz-sys",
+ "lz4-sys",
  "tikv-jemalloc-sys",
- "zstd-sys",
 ]
 
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