[lldb-dap] Make lldb-dap.executable-path machine specific

Change the scope [1] of lldb-dap.executable-path to
"machine-overridable":

> Machine specific settings that can be overridden by workspace or
> folder settings.

Practically speaking, this means that the path won't be synced across
machines and "(Not synced)" will show up next to the setting. I believe
it doesn't make sense to sync this setting (and I remember a bug report
where this caused trouble when using VS Code remotely), plus it matches
what clangd does for its corresponding setting.

[1] https://code.visualstudio.com/api/references/contribution-points#Configuration-property-schema

Author: JDevlieghere

lldb/tools/lldb-dap/package.json

@@ -74,7 +74,8 @@
         "lldb-dap.executable-path": {
           "scope": "resource",
           "type": "string",
-          "description": "The path to the lldb-dap binary."
+          "scope": "machine-overridable",
+          "description": "The path to the lldb-dap binary, e.g. /usr/local/bin/lldb-dap"
         },
         "lldb-dap.arguments": {
           "scope": "resource",