Rename maven install back to in MODULE.bazel

Fixes #21177

This PR essentially reverts #18641, which claimed

> Since protobuf is not contributing to user's JARs

This is not true since targets like `@com_google_protobuf//:protobuf_java` are meant to be consumed by other projects, therefore protobuf should not use a private maven install namespace. Otherwise, it leads to duplicated maven jars and classpath conflicts. See #21177 and bazel-contrib/rules_jvm_external#916 (comment)

The original warning message caused by multiple modules contributing to `maven` can be suppressed with bazel-contrib/rules_jvm_external#1393, which will be available in rules_jvm_external 6.8.

The PR use a repo mapping trick of `use_repo` to keep BUILD files intact, underlying both `protobuf_maven` and `protobuf_maven_dev` points to the universal `maven` install, while targets in `protobuf_maven_dev` are only available while protobuf is the root module and won't propagate to dependents.

PiperOrigin-RevId: 781031722

Author: protobuf-github-bot

MODULE.bazel

@@ -187,23 +187,24 @@ PROTOBUF_MAVEN_ARTIFACTS = [
 
 protobuf_maven = use_extension("@rules_jvm_external//:extensions.bzl", "maven")
 protobuf_maven.install(
-    name = "protobuf_maven",
     artifacts = PROTOBUF_MAVEN_ARTIFACTS,
     lock_file = "//:maven_install.json",
     repositories = [
         "https://repo1.maven.org/maven2",
         "https://repo.maven.apache.org/maven2",
     ],
 )
-use_repo(protobuf_maven, "protobuf_maven")
+
+# Use the default "maven" namespace because protobuf java targets are exposed to users
+# See https://github.com/protocolbuffers/protobuf/issues/21177
+use_repo(protobuf_maven, protobuf_maven = "maven")
 
 # Temporarily pin transitive dependency for https://github.com/bazelbuild/bazel/issues/24426
 bazel_dep(name = "re2", version = "2024-07-02.bcr.1")
 
 # Development dependencies
 protobuf_maven_dev = use_extension("@rules_jvm_external//:extensions.bzl", "maven", dev_dependency = True)
 protobuf_maven_dev.install(
-    name = "protobuf_maven_dev",
     artifacts = PROTOBUF_MAVEN_ARTIFACTS + [
         "com.google.caliper:caliper:1.0-beta-3",
         "com.google.guava:guava-testlib:32.0.1-jre",
@@ -220,7 +221,7 @@ protobuf_maven_dev.install(
         "https://repo.maven.apache.org/maven2",
     ],
 )
-use_repo(protobuf_maven_dev, "protobuf_maven_dev")
+use_repo(protobuf_maven_dev, protobuf_maven_dev = "maven")
 
 bazel_dep(name = "googletest", version = "1.15.2", dev_dependency = True)
 bazel_dep(name = "rules_buf", version = "0.3.0", dev_dependency = True)