chore(antithesis): Alter dogstatsd generation to is_malformed regime

Our previous approach to generating dogstatsd load for use in the
Antithesis rig was very Datadog/lading inspired: generate something
that is correct-by-construction and then bias the result to be
'interesting'. This works well but the biasing systematically avoids
conditions that are not-malformed -- that is, accepted by the SUT --
but are demonstrative of goofy behavior. This commit changes the
generator to be a hybrid of that approach with a state search approach.
We define a predicate `is_malformed` that confirms whether or not
a payload will be accepted by the SUT and then payloads which are not
malformed, however strange, are transmitted.

Author: blt

Cargo.lock

@@ -24,6 +24,7 @@ ryu = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 serde_yaml = { workspace = true }
+simdutf8 = { workspace = true }
 
 [dev-dependencies]
 proptest = { workspace = true }