New Parquet-Variant encoding (#7130)

## Summary

This PR introduces a new encoding to support Arrow's canonical extension
type, but does not integrate it with anything else.

It does include basic pieces like slice/take/filter, and it can (or at
least should) roundtrip with the equivalent arrow array.

## Testing

The encoding includes a bunch of basic tests, both for making sure it
roundtrips with arrow and for the various nullability cases.

---------

Signed-off-by: Adam Gutglick <adam@spiraldb.com>

Author: AdamGS

Cargo.lock

@@ -33,6 +33,7 @@ members = [
     "vortex-python",
     "vortex-tui",
     "vortex-web/crate",
+    "vortex-sqllogictest",
     "vortex-test/compat-gen",
     "vortex-test/e2e-cuda",
     "xtask",
@@ -49,13 +50,13 @@ members = [
     "encodings/zigzag",
     "encodings/zstd",
     "encodings/bytebool",
+    "encodings/parquet-variant",
     # Benchmarks
     "benchmarks/lance-bench",
     "benchmarks/compress-bench",
     "benchmarks/datafusion-bench",
     "benchmarks/duckdb-bench",
     "benchmarks/random-access-bench",
-    "vortex-sqllogictest",
 ]
 exclude = ["java/testfiles", "wasm-test"]
 resolver = "2"
@@ -184,6 +185,8 @@ opentelemetry-otlp = "0.31.0"
 opentelemetry_sdk = "0.31.0"
 parking_lot = { version = "0.12.3", features = ["nightly"] }
 parquet = "58"
+parquet-variant = "58"
+parquet-variant-compute = "58"
 paste = "1.0.15"
 pco = "1.0.1"
 pin-project-lite = "0.2.15"

Cargo.toml

@@ -0,0 +1,40 @@
+[package]
+name = "vortex-parquet-variant"
+authors = { workspace = true }
+categories = { workspace = true }
+description = "Vortex Parquet Variant array"
+edition = { workspace = true }
+homepage = { workspace = true }
+include = { workspace = true }
+keywords = { workspace = true }
+license = { workspace = true }
+readme = { workspace = true }
+repository = { workspace = true }
+rust-version = { workspace = true }
+version = { workspace = true }
+publish = false
+
+[lints]
+workspace = true
+
+[dependencies]
+arrow-array = { workspace = true }
+arrow-buffer = { workspace = true }
+arrow-schema = { workspace = true }
+chrono = { workspace = true }
+parquet-variant = { workspace = true }
+parquet-variant-compute = { workspace = true }
+prost = { workspace = true }
+vortex-array = { workspace = true }
+vortex-buffer = { workspace = true }
+vortex-error = { workspace = true }
+vortex-mask = { workspace = true }
+vortex-proto = { workspace = true }
+vortex-session = { workspace = true }
+
+[dev-dependencies]
+rstest = { workspace = true }
+vortex-array = { workspace = true, features = ["_test-harness"] }
+
+[package.metadata.cargo-machete]
+ignored = ["getrandom_v03"]