[monitor, theia] Consider not pulling in the `@theia/plugin-ext` dependency for the modal dialog

### Is your feature request related to a problem? Please describe.

Depending on `@eclipse-theiacloud/monitor-theia` unnecessarily pulls the following dependencies into the Theia-base app:

```jsonc
"@theia/bulk-edit": "1.59.0",
"@theia/callhierarchy": "1.59.0",
"@theia/console": "1.59.0",
"@theia/core": "1.59.0",
"@theia/debug": "1.59.0",
"@theia/editor": "1.59.0",
"@theia/editor-preview": "1.59.0",
"@theia/file-search": "1.59.0",
"@theia/filesystem": "1.59.0",
"@theia/markers": "1.59.0",
"@theia/messages": "1.59.0",
"@theia/monaco": "1.59.0",
"@theia/monaco-editor-core": "1.96.302",
"@theia/navigator": "1.59.0",
"@theia/notebook": "1.59.0",
"@theia/output": "1.59.0",
"@theia/plugin": "1.59.0",
"@theia/preferences": "1.59.0",
"@theia/scm": "1.59.0",
"@theia/search-in-workspace": "1.59.0",
"@theia/task": "1.59.0",
"@theia/terminal": "1.59.0",
"@theia/test": "1.59.0",
"@theia/timeline": "1.59.0",
"@theia/typehierarchy": "1.59.0",
"@theia/variable-resolver": "1.59.0",
"@theia/workspace": "1.59.0",
```

Consider a bare-minimum application that wishes to monitor user activity to time out the session prematurely; now, all these dependencies 👆 are pulled into the app just for a modal dialog.

### Describe the solution you'd like

`@eclipse-theiacloud/monitor-theia` does not pull in unnecessary dependencies or features.

### Describe alternatives you've considered

Pipe dream: there is a modal dialog in `@theia/core`; `@eclipse-theiacloud/monitor-theia` depends on `@theia/core`.

### Cluster provider

_No response_

### Additional information

_No response_

No source files or tests are named. Start by tracing the @eclipse-theiacloud/monitor-theia dependency and its modal-dialog imports, then compare whether @theia/core can provide the same dialog without @theia/plugin-ext. Done means the monitor package no longer pulls in the listed unnecessary Theia dependencies while its modal dialog still works.

Written by the indexing model from the issue text.