Plugins: sandboxed Luau plugins in mods, phase 1 (the host, and the base, console and storage APIs)

A mod with a reskate-plugin.json is a plugin: Luau scripts that run in their own VM, with only
the reskate API ReSkate registers for them. Luau 0.741 is vendored in External/luau (the VM and
compiler only: no native code generation, no loadstring, io or C modules).

- Limits: 64 MB of memory, 50 ms a call, 2 ms a tick on average (over it for 3 s stops it),
  more than 5 errors in 10 s stops it, 50 log lines a second. A plugin over a limit cannot catch
  it in a pcall and carry on.
- API: reskate.log, on (load, unload, tick, level_loaded, level_unloading), timers, the level,
  its own package's files and JSON, require inside the package; console.command and print
  ("console"); storage get, set, add and keys ("storage"), 1 MB in
  %LOCALAPPDATA%\ReSkate\Plugins\<mod>\storage.json.
- Found every 2 s among the mods mods.json leaves on: switching a mod, or changing a plugin's
  files, loads, unloads or reloads it without a restart. A package holding a program is refused.
- plugin list, commands, reload, off and on in the console. A plugin cannot take a name of
  ReSkate's own commands.
- Tests: DINGOSDK_BUILD_PLUGIN_TESTS, including plugins written to break the sandbox.

Runtime/runtime_init.cpp

@@ -30,6 +30,7 @@
 #include "Extension/Assets/map_download.h"
 #include "Extension/Boot/offline_boot.h"
 #include "Extension/HallOfMeat/hall_of_meat.h"
+#include "Extension/Plugins/plugin_runtime.h"
 #include "Extension/RoadRash/road_rash.h"
 #include "Extension/BoardBreak/board_break.h"
 #include "Extension/Skater/grind_exit_control.h"
@@ -444,6 +445,8 @@ extern "C" __declspec(dllexport) BOOL WINAPI DingoSDKDebugInitialize() {
         const bool camera_hook = dingosdk::start_camera_observer(r.base);
         record("{\"event\":\"camera_observer_initialized\",\"active\":" + std::string(camera_hook ? "true" : "false") + "}");
         (void)dingosdk::start_no_bail(r.base);
+        const bool plugins = dingosdk::plugins::start();
+        record("{\"event\":\"plugins_initialized\",\"active\":" + std::string(plugins ? "true" : "false") + "}");
         const bool meat = dingosdk::hall_of_meat::start(r.base);
         record("{\"event\":\"hall_of_meat_initialized\",\"active\":" + std::string(meat ? "true" : "false") + "}");
         const bool rash = dingosdk::road_rash::start(r.base);