Settings Import: Add Support for Workbench

[samclark2015]

Issue #1639 implemented a method for users to import VSCode settings into Positron on desktop. This will be extended to support Workbench. Some additional tasks need to be resolved:

• A mechanism for locating correct VSCode settings on Workbench is necessary
• Better support for merging settings is required in order to support admin-defined default user settings (more likely a conflict will occur on Workbench because of this)
• Remove logic from contribution which disables on web

Workbench Settings location

• Admin can configure this path in /etc/rstudio/vscode.conf using the user-data-dir key.
• This needs to be made accessible to Positron instances (env var?).
• Then, setting will live in ./User/settings.json per usual.

Workbench Settings merge

• Prefer admin's default Positron settings over incoming user's VSCode settings.
• Really need merge interface to work to support this well.

[testlabauto]

Verified Fixed

Positron Version(s) : Positron Version: 2025.06.0 build 107
OS Version          : ubuntu

Test scenario(s)

Verified on palm. Started a vscode session, then a positron session and dialog appeared as expected.

Link(s) to TestRail test cases run or created: