[Doc] Improve rust analyzer section, distinguishing bzlmod and WORKSPACE (#3365)

The documentation for the `rust-analyzer` section is outdated, and
realtive to the WORKSPACE approach. i tried improving it slightly,
distinguishing the bzlmod approach. Right now, calling
`rust_analyzer_dependencies()` when using bzlmod seems to throw an
error. References issue #2997

---------

Co-authored-by: UebelAndre <github@uebelandre.com>

Author: bertulli

docs/rust_analyzer.vm

@@ -10,23 +10,46 @@ The `rust_analyzer` rules facilitate both approaches.
 ## rust-project.json approach
 ### Setup
 
-First, ensure `rules_rust` is setup in your workspace. By default, `rust_register_toolchains` will
-ensure a [rust_analyzer_toolchain](#rust_analyzer_toolchain) is registered within the WORKSPACE.
+#### Bzlmod
 
-Next, load the dependencies for the `rust-project.json` generator tool:
+First, ensure `rules_rust` is setup in your workspace:
 
 ```python
-load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")
+# MODULE.bazel
 
-rust_analyzer_dependencies()
+# See releases page for available versions:
+# https://github.com/bazelbuild/rules_rust/releases
+bazel_dep(name = "rules_rust", version = "{SEE_RELEASES}")
+```
+
+Bazel will create the target `@rules_rust//tools/rust_analyzer:gen_rust_project`, which you can build
+with
+
+```
+bazel run @rules_rust//tools/rust_analyzer:gen_rust_project
 ```
 
-Finally, run `bazel run @rules_rust//tools/rust_analyzer:gen_rust_project`
 whenever dependencies change to regenerate the `rust-project.json` file. It
 should be added to `.gitignore` because it is effectively a build artifact.
 Once the `rust-project.json` has been generated in the project root,
 rust-analyzer can pick it up upon restart.
 
+#### WORKSPACE
+
+Alternatively, you can use the legacy WORKSPACE approach. As with Bzlmod, ensure `rules_rust` is
+setup in your workspace.
+
+Moreover, when loading the dependencies for the tool, you should call the function `rust_analyzer_dependencies()`:
+
+```python
+load("@rules_rust//tools/rust_analyzer:deps.bzl", "rust_analyzer_dependencies")
+
+rust_analyzer_dependencies()
+```
+
+Again, you can now run `bazel run @rules_rust//tools/rust_analyzer:gen_rust_project`
+whenever dependencies change to regenerate the `rust-project.json` file.
+
 For users who do not use `rust_register_toolchains` to register toolchains, the following can be added
 to their WORKSPACE to register a `rust_analyzer_toolchain`. Please make sure the Rust version used in
 this toolchain matches the version used by the currently registered toolchain or the sources/documentation