chore: Add serde performance tests to protocol test suite

[jbelkins]

Description of changes

Adds a performance testing target to protocol tests:

• A shape is code-generated along with its serde methods.
• Three arrays of test objects are prepared, each an order of magnitude larger than the one before.
• The test data is converted to JSON data.
• The JSON data is deserialized back into an array of test objects, using the following:
  • SmithyJSON Reader
  • Swift Decodable / JSONDecoder
• Time measurements are taken with Xcode on the deserialization process.
• The deserialized test objects are compared to the originals, to verify that deserialization was accurate.

These tests may be extended with new Smithy protocols and other serde methods in the future.

New/existing dependencies impact assessment, if applicable

No new dependencies were added to this change.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[jbelkins]

CI is failing due to the JSON double decoding issue:
smithy-lang/smithy-swift#896

Tests should pass once that merges.