feat(trust): let users add trusted folders from settings (#1812)

* feat(trust): let users add trusted folders from settings

The trusted-locations check already matches projects by path prefix, but
the only way to populate it was the "Trust projects in…" checkbox on the
first-open dialog — a folder could never be trusted ahead of time.

Add a project_trust_add_location command that canonicalizes the picked
directory, rejects non-directories, and deduplicates, plus an "Add
folder…" button on the Project Trust settings page backed by the native
directory picker.

Fixes #1743

* fix(trust): translate the trusted-location additions into Chinese

The zh source-text catalog must cover every literal UI text; the three
new strings in the trusted-locations settings page were missing.

src/platform/locales/text/zh.json

@@ -232,6 +232,8 @@
   "Activate virtualenv": "激活 virtualenv",
   "Add": "添加",
   "Add Column": "添加列",
+  "Add Trusted Location": "添加受信任的位置",
+  "Add folder…": "添加文件夹…",
   "Add Field Watchpoint": "添加字段监视点",
   "Add File to Git": "将文件添加到 Git",
   "Add GitHub Pattern": "添加 GitHub 模式",
@@ -3155,6 +3157,7 @@
   "(empty line)": "（空行）",
   "Name cannot be empty": "名称不能为空",
   "Every scope needs a name": "每个范围都需要名称",
+  "Every project inside a trusted location is trusted without asking.": "受信任的位置内的每个项目都会被信任，不再询问。",
   "Scopes": "范围",
   "Add Scope": "添加范围",
   "Remove Scope": "移除范围",