feature: Implement Shape::widen which enables widening a Shape to…

… fit a provided `AsNode`. This sets the groundwork for performantly keeping track of a running inferred schema in the combiner.

Of note, the schemas "inferred" by `widen()` are maximally strict:
* By default, newly inferred objects have have `additionalProperties: false`.
* Object fields initially have `required: true` until we encounter a document missing that field, at which point it will be downgraded to `required: false`

The next piece of work is implementing the stubbed-out `enforce_field_count_limits`. With that, we should have everything we need to implement the running inferred schema and emit it to the ops logs. Also of note is that the `reduce: flow-inferred-schema-merge` reduction annotation implementation can and should also use `enforce_field_count_limits`, as it's possible for itra-transaction documents to not exceed the limits while inter-transaction documents do, and we care about limiting both of those cases.

Cargo.toml

@@ -197,6 +197,8 @@ tonic-build = "0.9"
 
 warp = "0.3.3"
 
+pretty_assertions = "1.4.0"
+
 [profile.release]
 incremental = true
 debug = 0          # Set this to 1 or 2 to get more useful backtraces in debugger.

crates/doc/Cargo.toml

@@ -43,8 +43,9 @@ rand_distr = { workspace = true }
 serde-transcode = { workspace = true }
 serde_json = { workspace = true }
 serde_yaml = { workspace = true }
+pretty_assertions = { workspace = true }
 
 [features]
 default = ["combine"]
 
-combine = ["lz4"]
+combine = ["lz4"]