Modules containing valid Markdown in their description or README.md could cause Odoo to crash during startup or module updates if the content confused the reStructuredText (RST) parser.

### Steps to reproduce

1. Create a module with a manifest like this:

    ```py
    {
        'name': 'base',
        'description': """
        ....
    """,
    }
    ```

2. Start the Odoo server or attempt to install or update update the module.
3. The server crashes:

    ```
    docutils.utils.SystemMessage: (SEVERE/4) Unexpected section title or transition.
    ```

### Cause

The crash occurs during the execution of the `_get_desc` method in the `ir.module.module` model, which computes the `description_html` field.

When Odoo processes a module, it checks for a pre-rendered HTML description at `static/description/index.html`. If this file is missing, the `_get_desc` method attempts to generate HTML from the module's `description` field (often populated from the `README.md` file) by calling the `docutils.core.publish_string` function.

The **docutils** library is designed specifically for **reStructuredText (RST)**. If the input text contains structural patterns that violate RST rules—such as inconsistent header levels or "transitions" in invalid contexts—docutils flags a severe error and raises a `docutils.utils.SystemMessage` exception.

### Fix

This commit handles these exceptions and falls back to a raw text rendering. It also improves the logic by removing the restriction that prevented non-application modules from rendering their description via RST.

opw-5424131

Forward-Port-Of: odoo/odoo#243517