Update All feature for plugins

### Describe the feature or problem you'd like to solve

I'd like to update all of my plugins in one command

### Proposed solution

Accept new parameters to the /plugin update command to update all plugins to their latest versions.

### Example prompts or workflows

/plugin update all
/plugin update *

### Additional context

_No response_

Start at the /plugin update command entry point and trace how a plugin name is parsed and updated. Compare the requested all and * forms with the existing single-plugin flow. Done means both examples update every plugin to its latest version without changing single-plugin behavior.

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