RStudio Keymap shortcuts are visible even with keymap disabled

[jmcphers]

The RStudio Keymap shortcuts are visible all the time, even with the keymap disabled. They wind up in menus (see #3847), and are also visible in the key mappings dialog.

This happens because the RStudio Keymap extension registers its shortcuts declaratively, as part of the extension's package JSON.

positron/extensions/positron-rstudio-keymap/package.json

Lines 51 to 59 in 8fa8041

	"keybindings": [
	{
	"mac": "cmd+shift+n",
	"win": "ctrl+shift+n",
	"linux": "ctrl+shift+n",
	"key": "ctrl+shift+n",
	"when": "config.rstudio.keymap.enable",
	"command": "r.createNewFile"
	},

This is the established pattern for keymaps extensions in the ecosystem.

However, because the RStudio Keymap is a built-in extension, it is always installed and always activated. In order to prevent the keymap from also always being active, we guard each mapping with config.rstudio.keymap.enable, so it only engages when the "RStudio Keymap" setting is on.

This doesn't provide a clean experience; we need to prevent these keymappings from leaking when the keymap is disabled.

Options:

• build the keymap as a VSIX and bundle it (as in Python: Investigate building positron-python extension as a VSIX instead of a built-in #2271), then install on demand in some way
• build the keymap as a VSIX, publish it to OpenVSX, and tell people to install it from the marketplace if they want RStudio keybindings
• find a way to actually activate/deactivate the extension (even though it's built in) in accordance with the setting
• put the keybindings somewhere other than in an extension, e.g. when the setting is on, dynamically register them from somewhere in the core
• run away from home and live in the woods