Migrate to Bzlmod

[pcj]

This PR updates closure-template to use the bzlmod for dependency management.

Details:

• MODULE.bazel added. Direct bazel_deps are at latest versions. WORKSPACE
  file is empty, can be deleted.
• Protobuf updated to 32.0.
• .bazelversion: updated to 8.4.1.
• java language version updated to 17.
• The bulk of file changes reflect the name change of @maven to
  @maven_closure_templates. Because closure-templates can be used as a bzlmod
  dependency, the @maven namespace is problematic becuase entries from
  multiple bzlmod workspaces can contribute to it. Therefore, dependencies for
  this repo have been moved into a separate namespace.
• java/src/com/google/template/soy/data/ProtoFieldInterpreter.java: small
  change to adjust for the now-deleted java package
  com.google.protobuf.Descriptors.FileDescriptor.Syntax.
• third_party/google/safe-html-types: the maven artifact
  com.google.common.html.types:types:1.0.8 is the "latest" version available
  via maven central. It was published Nov 09, 2017 and embeds generated code
  that is no longer compatible with more recent versions of protobuf. The
  source repository https://github.com/google/safe-html-types was archived Dec 2023.
  As a result, the state of the files in last commit of
  google/safe-html-types has been vendored into this repo and the
  java_proto_library builds from source (see
  third_party/google/safe-html-types/proto/webutil/html/types/BUILD.bazel). A
  maven.override is used to map the coordinate
  com.google.common.html.types:types to
  //third_party/google/safe-html-types/java/com/google/common/html/types.