go_proto_library: Issue/New Feature for output path generation.

Hello, I am unsure whether this is an issue or a new feature request (details follow this introduction). The following describes an issue I encountered with your protobuf plugin when I tried to generate using ConnectRPC's plugin in Bazel 7/bzlmod. Working with the ConnectRPC team, we developed a patch-based solution. I have created a repository for my project with the patch and have donated it to the public domain at https://github.com/abitofhelp/connect-go-example. It would be great if we could add what the patch provides to rules_go. I hope that this information and example code is helpful.

### What version of rules_go are you using?
0.47.1

### What version of gazelle are you using?
0.36.0

### What version of Bazel are you using?
7.2.0

### Does this issue reproduce with the latest releases of all the above?
Yes

### What operating system and processor architecture are you using?
MacOS (Sonoma 14.5), AMD64

### Any other potentially useful information about your toolchain?
Golang 1.22.3
rules_buf 0.2.0

### What did you do?
I created a client/server Go solution that builds with Bazel 7/bzlmod and uses ConnectRPC.
I configured the Bazel build to generate the protobuf file without Connect's proto plugin.
I configured go_proto_compiler to use Connect's plugin to generate the client/server stubs.

### What did you expect to see?
Using Bazel, I generated the protobuf file and it was placed in the correct directory:
* bazel-bin/greet/v1/greetv1_go_proto_/github.com/abitofhelp/connect-go-example/gen/greet/v1/greet.go

Using Bazel, I tried to generate Connect's file in the following location, but nothing was created:
* bazel-bin/greet/v1/greetv1_go_proto_/github.com/abitofhelp/connect-go-example/gen/greet/v1/greetv1connect/greet.connect.go
Notice that Connect's code is in a separate module from the protobuf code, hence it needs to be in a subdirectory for Connect's module.

### What did you see instead?
Using Bazel, I tried to generate Connect's file and nothing was generated.
I contacted Connect's team for assistance debugging the issue.

#########################
## ADDITIONAL INFORMATION
#########################
Working with ConnectRPC's team, we determined rules_go assumes that generated files go into a single directory (i.e. '/gen/greet/v1'). However, if Connect's generated code is in a separate module from Protobuf's code, it must be placed in a subdirectory named as Connect's generated module (greetv1connect). The expected path for the Connect's generated file would be the following:
* bazel-bin/greet/v1/greetv1_go_proto_/github.com/abitofhelp/connect-go-example/gen/greet/v1/greetv1connect/greet.connect.go

In order to support this feature, we created a patch that added a new field to go_proto_library, and it is working properly. The BUILD.bazel file next to the related .proto file has the following go_proto_library blocks. Note the new field: 'overrideimportpath'.

```
# Generate the greet.connect.pb.go file, which imports greet.pb.go.
go_proto_library(
name = "greetv1_connect_go_proto",
compilers = [
":connect_go_proto_compiler",
],
importpath = "github.com/abitofhelp/connect-go-example/gen/greet/v1",
overrideimportpath = "github.com/abitofhelp/connect-go-example/gen/greet/v1/greetv1connect",
proto = ":greetv1_proto",
visibility = ["//visibility:public"],
deps = [":greetv1_go_proto"],
)

# Generate the greet.pb.go file.
go_proto_library(
name = "greetv1_go_proto",
importpath = "github.com/abitofhelp/connect-go-example/gen/greet/v1",
proto = ":greetv1_proto",
visibility = ["//visibility:public"],
)
```
FWIW: When I use protoc or 'buf generate proto' rather than bazel to build the solution, they generate the pb and connect files in the proper directory structure.

Start with the donated connect-go-example repository and its BUILD.bazel go_proto_library declarations, then compare the overrideimportpath patch with rules_go's existing output-path handling. Reproduce the Bazel 7/bzlmod generation case; done means the Connect file is produced under the requested greetv1connect subdirectory alongside the protobuf output.

Written by the indexing model from the issue text.