Support latest PXT with GC (#1798)

* Enable gc and basic compilation fixes

* Add missing GC stuff

* Set microbit-dal version

* Disable jacdac in servo

* UTF fixes

* TS build fixes

* Auto-generated files update

* We only seem to have that much

* Fix for new new compiler

* Account for uninitialized scheduler

* Intialize memory allocator

* bump references

* updated package

* Set image tag, requires https://github.com/Microsoft/pxt/pull/5262

* updated project summaries

* Fixing block tests

pxtarget.json

@@ -36,6 +36,9 @@
         "flashCodeAlign": 1024,
         "floatingPoint": true,
         "taggedInts": true,
+        "utf8": false,
+        "gc": true,
+        "imageRefTag": 9,
         "patches": {
             "0.0.0 - 1.0.0": [
                 {
@@ -218,7 +221,7 @@
         "yottaTarget": "bbc-microbit-classic-gcc",
         "yottaCorePackage": "microbit",
         "githubCorePackage": "lancaster-university/microbit",
-        "gittag": "v2.1.1",
+        "gittag": "pxtgc-0",
         "serviceId": "microbit",
         "dockerImage": "pext/yotta:latest"
     },