Update expected generated code in tests (#96)

Motivation:

grpc-swift 2.3.0 updated the generated code to include the type of an
RPC. The expectations in some code gen tests in this package are now
incorrect.

Modifications:

- Bump the required version
- Update test expectation

Result:

Tests pass

Support Protobuf Edition 2024 (#93)

Motivation:

Protobuf edition 2024 has been out for a little while now, we should
support it. Happily this is just a case of bumping the supported range.

Modifications:

- Widen the supported range
- Add an integration test

Result:

Users can generate gRPC code for protos which use `edition = "2024"`

Bump grpc-swift-2 depenendency requirement (#91)

Motivation:

A recent release of grpc-swift-2 added a few sendable annotations to the
generated code. The expected code in our tests is now incorrect so CI is
failing.

Modifications:

- Bump version
- Update test expectations
- Regenerate

Result:

CI passes

Fix warnings in command plugin (#87)

Motivation:

The command plugin had a couple of warnings as vars weren't mutated.

Modifications:

- Change some vars to lets
- Remove an unused string

Result:

No warnings

Regenerate protos after update (#85)

Motivation:

swift-protobuf released a new version which modified generated code
slightly. Our CI job for checking up-to-date generated code now fails.

Modifications:

- Update generated code

Result:

CI passes

Add deprecation warnings (#72)

Motivation:

gRPC Swift v2 has moved to a new repo, grpc-swift-2 and as a result this
package has a new major version. That's not all that discoverable.

Modifications:

Deprecate commonly used high-level types with a link to a forums post
explaining the move.

Result:

Users are notified about the move

Move to grpc-swift-2 (#70)

Motivation:

To support incremental migration, v2 has moved to the 'grpc-swift-2'
package.

Modifications:

- Update dependencies
- Update generated code
- Re-baseline availability
- Rename 'protoc-gen-grpc-swift' to 'protoc-gen-grpc-swift-2'

Result:

Easier to migrate from gRPC Swift 1 to 2

Move availability inline (#68)

Motivation:

It's hard for packages to incrementally adopt gRPC with platforms in the
package manifest as it requires packages to include platforms in their
manifest or mint a new major version.

Modifications:

- Move platform availability onto source code
- Check annotations in CI

Result:

Easier to adopt

Fix GoogleRPCStatus encoding/decoding (#58)

Motivation:

The 'rich' error model packs a google.rpc.status protobuf message into
the trailing metadata of an RPC. This should just be the base64 encoded
bytes of the serialzed message. At the moment this is packed within a
google.protobuf.any and then added to the metadata which doesn't interop
well with other languages.

Modifications:

- Remove the indirection
- Add methods for serializing/deserializing the RPC status wrapper

Result:

Better interop

Add command plugin to package products (#52)

Motivation:

The command plugin needs to be a product in order for it to be used.

Modifications:

- Add it to the products
- Give it the same name as the command, otherwise diagnostics (like
SwiftPM asking for permission to write to the package dir) will use a
different name which isn't obvious.
- Fix a few build warnings.

Result:

- Command plugin can be used