Code review comment for ubuntu-security-tools:iosifache/semgrep-rules-manager

I think we can reuse the logic and flow that is already there for tool installation instead of introducing extra helpers. The new requirement of semgrep-rules-manager for example can be handled in verify_requirements() or maybe even better in uaudit_install_dependencies() directly:

```python
def uaudit_install_dependencies():
    dependencies = {}
    for tool in static_analysis_tools:
        dependencies[tool.name] = tool.install_cmd()

+ dependencies["semgrep-rules-manager"] = ["snap", "install", "semgrep-rules-manager"]

    for tool, cmd_args in dependencies.items():
        if is_program_installed(tool):
            debug(f'{tool} is already installed in the system')
        else:
            install_tool(cmd_args, tool)

```

Then we would only need to prompt for the extra sources via ask_for_custom_semgrep_rules() -> download_custom_semgrep_rules() and remove the ensure_installed_semgrep_rules_manager() method.