feat: Introduce icp:sync-plugin@0.2.0

[adamspofford-dfinity]

Update the sync plugin interface to 0.2.0. Both versions are supported side-by-side depending on what version the plugin imports (based on actual version metadata, not probing for e.g. field names).

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[Copilot]

Pull request overview

Introduces sync-plugin ABI v0.2.0 while preserving compatibility with v0.1.x plugins through metadata-based runtime dispatch.

Changes:

• Adds parallel v1/v2 WIT bindings and ABI detection.
• Adds a legacy plugin fixture and compatibility test.
• Updates dependencies and documentation.

Reviewed changes

Copilot reviewed 10 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
docs/concepts/sync-plugins.md	Documents interface versioning.
crates/icp-sync-plugin/tests/fixtures/test-plugin-v1/src/lib.rs	Implements legacy test plugin.
crates/icp-sync-plugin/tests/fixtures/test-plugin-v1/Cargo.toml	Configures legacy fixture.
crates/icp-sync-plugin/tests/fixtures/test-plugin-v1/Cargo.lock	Locks fixture dependencies.
crates/icp-sync-plugin/tests/fixtures/test-plugin-v1/build.rs	Tracks legacy WIT changes.
crates/icp-sync-plugin/sync-plugin.wit	Advances current ABI to v0.2.0.
crates/icp-sync-plugin/sync-plugin-v1.wit	Preserves the v0.1.0 contract.
crates/icp-sync-plugin/src/runtime.rs	Detects and dispatches ABI versions.
crates/icp-sync-plugin/DESIGN.md	Documents parallel ABI handling.
crates/icp-sync-plugin/Cargo.toml	Adds semver dependency.
crates/icp-sync-plugin/build.rs	Builds both test fixtures.
Cargo.lock	Records the dependency update.

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