feat(settings): log without throwing if default value is provided

Problem:
If a user setting has the wrong type, `Settings.instance.get` throws an
exception, even if a `defaultValue` is provided. We almost never want
that behavior. Example:

    Settings.instance.get<Object>('files.exclude', Number, 42)

Solution:
Copy the logic from `AnonymousSettings.get()`.

TODO: see if we can de-duplicate the logic.

src/shared/settings.ts

@@ -41,9 +41,18 @@ export class Settings {
     public get<T>(key: string, type: TypeConstructor<T>): T | undefined
     public get<T>(key: string, type: TypeConstructor<T>, defaultValue: T): T
     public get<T>(key: string, type?: TypeConstructor<T>, defaultValue?: T) {
-        const value = this.getConfig().get(key, defaultValue)
+        try {
+            const value = this.getConfig().get(key, defaultValue)
+
+            return !type || value === undefined ? value : cast(value, type)
+        } catch (e) {
+            if (arguments.length === 1) {
+                throw ToolkitError.chain(e, `Failed to read key "${key}"`)
+            }
+            getLogger().error(`using default for key "${key}", read failed: %s`, (e as Error).message)
 
-        return !type || value === undefined ? value : cast(value, type)
+            return defaultValue
+        }
     }
 
     /**