Starlarkified proto_library doesn't support target names containing slashes

### Description of the bug:

This check: https://github.com/bazelbuild/bazel/blob/80235380833c61bc47dd14efb8fe1c395e17316a/src/main/starlark/builtins_bzl/common/proto/proto_info.bzl#L78-L79 fails if a target name contains a `/` character.

This was allowed in Bazel 6, but will be broken in Bazel 7.

### Which category does this issue belong to?

_No response_

### What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

`WORKSPACE`:
```starlark
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
name = "rules_proto",
sha256 = "dc3fb206a2cb3441b485eb1e423165b231235a1ea9b031b4433cf7bc1fa460dd",
strip_prefix = "rules_proto-5.3.0-21.7",
urls = [
"https://artifacts.apple.com/github.com/bazelbuild/rules_proto/archive/5.3.0-21.7.tar.gz",
],
)

load("@rules_proto//proto:repositories.bzl", "rules_proto_dependencies", "rules_proto_toolchains")

rules_proto_dependencies()
rules_proto_toolchains()
```

`dir/BUILD.bazel`:
```starlark
dir/BUILD.bazel
load("@rules_proto//proto:defs.bzl", "proto_library")

proto_library(
name = "child/person_proto",
srcs = ["child/person.proto"],
strip_import_prefix = "/dir",
)

java_proto_library(
name = "java_child",
deps = [":child/person_proto"],
)
```

The following succeeds:
```
USE_BAZEL_VERSION=6.3.2 bazel build dir/...
```

The following fails:
```console
% USE_BAZEL_VERSION=7.0.0-pre.20230823.4 bazel build dir/...
Starting local Bazel server and connecting to it...
INFO: Invocation ID: 93bff424-c310-472b-b71e-9ab196655a3f
ERROR: [redacted]/BUILD.bazel:3:14: in proto_library rule //dir:child/person_proto:
Traceback (most recent call last):
File "/virtual_builtins_bzl/common/proto/proto_library.bzl", line 80, column 27, in _proto_library_impl
File "/virtual_builtins_bzl/common/proto/proto_info.bzl", line 144, column 24, in ProtoInfo
File "/virtual_builtins_bzl/common/proto/proto_info.bzl", line 79, column 17, in _create_proto_info
Error in fail: proto_path needs to be formed like '_virtual_imports/target_name'
ERROR: [redacted]/BUILD.bazel:3:14: Analysis of target '//dir:child/person_proto' failed
ERROR: Analysis of target '//dir:child/person_proto' failed; build aborted
INFO: Elapsed time: 3.127s
INFO: 0 processes.
ERROR: Build did NOT complete successfully
Loading: 36 packages loaded
Fetching repository @local_jdk; starting
```

### Which operating system are you running Bazel on?

macOS

### What is the output of `bazel info release`?

release 7.0.0-pre.20230823.4

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse master; git rev-parse HEAD` ?

_No response_

### Is this a regression? If yes, please try to identify the Bazel commit where the bug was introduced.

711f1b0e2496a189ed4d61ce321a91fa0f5f09a8

### Have you found anything relevant by searching the web?

_No response_

### Any other information, logs, or outputs that you want to share?

_No response_