Simplify debug launcher UI (#31928)

This PR updates the name of the `NewSessionModal` to `NewProcessModal`
(to reflect it's new purpose), changes the tabs in the modal to read
`Run | Debug | Attach | Launch` and changes the associated types in code
to match the tabs. In addition, this PR adds a few labels to the text
fields in the `Launch` tab, and adds a link to open the associated
settings file. In both debug.json files, added links to the zed.dev
debugger docs.

Release Notes:

- Debugger Beta: Improve the new process modal

assets/settings/initial_debug_tasks.json

@@ -1,3 +1,7 @@
+// Some example tasks for common languages.
+//
+// For more documentation on how to configure debug tasks,
+// see: https://zed.dev/docs/debugger
 [
   {
     "label": "Debug active PHP file",

assets/settings/initial_local_debug_tasks.json

@@ -0,0 +1,5 @@
+// Project-local debug tasks
+//
+// For more documentation on how to configure debug tasks,
+// see: https://zed.dev/docs/debugger
+[]