Add arrow-avro SchemaStore and fingerprinting (#8039)

# Which issue does this PR close?

- Part of #4886

- Pre-work for #8006

# Rationale for this change

Apache Avro’s [single object
encoding](https://avro.apache.org/docs/1.11.1/specification/#single-object-encoding)
prefixes every record with the marker `0xC3 0x01` followed by a `Rabin`
[schema fingerprint
](https://avro.apache.org/docs/1.11.1/specification/#schema-fingerprints)
so that readers can identify the correct writer schema without carrying
the full definition in each message.
While the current `arrow‑avro` implementation can read container files,
it cannot ingest these framed messages or handle streams where the
writer schema changes over time.

The Avro specification recommends computing a 64‑bit CRC‑64‑AVRO (Rabin)
hashed fingerprint of the [parsed canonical form of a
schema](https://avro.apache.org/docs/1.11.1/specification/#parsing-canonical-form-for-schemas)
to look up the `Schema` from a local schema store or registry.

This PR introduces **`SchemaStore`** and **fingerprinting** to enable:

* **Zero‑copy schema identification** for decoding streaming Avro
messages published in single‑object format (i.e. Kafka, Pulsar, etc)
into Arrow.
* **Dynamic schema evolution** by laying the foundation to resolve
writer reader schema differences on the fly.

**NOTE:**  Integration with `Decoder` and `Reader` coming in next PR.

# What changes are included in this PR?

| Area | Highlights |
| ------------------- |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
| **`schema.rs`** | *New* `Fingerprint`, `SchemaStore`, and
`SINGLE_OBJECT_MAGIC`; canonical‑form generator; Rabin fingerprint
calculator; `compare_schemas` helper. |
| **`lib.rs`** | `mod schema` is now `pub` |
| **Unit tests** | New tests covering fingerprint generation, store
registration/lookup, unknown‑fingerprint errors, and interaction with
UTF8‑view decoding. |
| **Docs & Examples** | Extensive inline docs with examples on all new
public methods / structs. |


# Are these changes tested?

Yes.  New tests cover:

1. **Fingerprinting** against the canonical examples from the Avro spec
2. **`SchemaStore` behavior** deduplication, duplicate registration, and
lookup.

# Are there any user-facing changes?

N/A

Author: jecsand838

arrow-avro/Cargo.toml

@@ -56,6 +56,7 @@ bzip2 = { version = "0.6.0", optional = true }
 xz = { version = "0.1", default-features = false, optional = true }
 crc = { version = "3.0", optional = true }
 uuid = "1.17"
+strum_macros = "0.27"
 
 [dev-dependencies]
 arrow-data = { workspace = true }

arrow-avro/src/lib.rs

@@ -33,10 +33,10 @@
 /// Implements the primary reader interface and record decoding logic.
 pub mod reader;
 
-// Avro schema parsing and representation
-//
-// Provides types for parsing and representing Avro schema definitions.
-mod schema;
+/// Avro schema parsing and representation
+///
+/// Provides types for parsing and representing Avro schema definitions.
+pub mod schema;
 
 /// Compression codec implementations for Avro
 ///