[Feature request] Use default settings in code for executorMap settings

**Is your feature request related to a problem? Please describe.**
Setting custom executorMap settings requires the full map to be present in your vscode config, whether it's changed or not.

**Describe the solution you'd like**
I'd like the code to use default settings whenever the value is not found in settings.json. This could be done at runtime by determining the map using object spreading (ie `executorMap = {...defaultExecutorMap, ...vscodeExecutorMap}`).
This change would allow settings.json to only contain *changed* entries, rather than all of the entries.

Locate the extension code that reads executorMap from VS Code settings and find where the default executor map is defined or assembled. Verify behavior with a partial settings map: changed entries should override defaults while omitted entries remain available, and existing executor behavior should continue to work.

Scritto dal modello di indicizzazione a partire dal testo della issue.