Use absolute import paths in option go_package

[sloretz]

This changes option go_package to use absolute import paths instead of relative ones. This fixes two build issues when using this library with Bazel via bazel_gazelle.

Example build errors fixed by this change:

ERROR: /home/sloretz/projects/bg_bug/streaming_service/BUILD:13:17: GoCompilePkg streaming_service/streaming_service_go_proto.a failed: (Exit 1): builder failed: error executing GoCompilePkg command (from target //streaming_service:streaming_service_go_proto) bazel-out/k8-opt-exec-ST-d57f47055a04/bin/external/rules_go++go_sdk+main___download_0/builder_reset/builder compilepkg -sdk external/rules_go++go_sdk+main___download_0 -goroot ... (remaining 67 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
bazel-out/k8-fastbuild/bin/streaming_service/streaming_service_go_proto_/bg_bug/streaming_service/streaming_service_go_proto/streaming_service.pb.go:10:4: could not import ./openapiv3 (open : no such file or directory)
compilepkg: error running subcommand external/rules_go++go_sdk+main___download_0/pkg/tool/linux_amd64/compile: exit status 2

ERROR: /home/sloretz/.cache/bazel/_bazel_sloretz/7f1c610792df1dcd4df92ba962d4dced/external/gazelle++go_deps+com_github_google_gnostic_models/extensions/BUILD.bazel:19:11: GoCompilePkg external/gazelle++go_deps+com_github_google_gnostic_models/extensions/extensions.a [for tool] failed: (Exit 1): builder failed: error executing GoCompilePkg command (from target @@gazelle++go_deps+com_github_google_gnostic_models//extensions:extensions) bazel-out/k8-opt-exec-ST-1be4dcb80a27/bin/external/rules_go++go_sdk+main___download_0/builder_reset/builder compilepkg -sdk external/rules_go++go_sdk+main___download_0 -goroot ... (remaining 29 arguments skipped)

Use --sandbox_debug to see verbose messages from the sandbox and retain the sandbox build root for debugging
external/gazelle++go_deps+com_github_google_gnostic_models/extensions/extensions.go:40:14: undefined: ExtensionHandlerRequest
external/gazelle++go_deps+com_github_google_gnostic_models/extensions/extensions.go:49:15: undefined: ExtensionHandlerResponse
compilepkg: error running subcommand external/rules_go++go_sdk+main___download_0/pkg/tool/linux_amd64/compile: exit status 2
Use --verbose_failures to see the command lines of failed build steps.

I don't know enough about golang to be able to explain why this fixes the issue 🤷

[Jefftree]

Thank you! This follows best practices of using absolute paths