fix(gui): Strictly enforce UI types with Typescript (#678)

* fix(gui): we were not checking for null everywhere

* add more null checks, enable tsconfig strict

* remove dead code

* more nullish checks

* remove unused JSONViewTree.tsx

* fix a bunch of small typescript lints

* add explanations as to why LabeledMoneroAddress.address is non-nullish but we pass in null due to typeshare limitation

* remove @mui/lab from yarn.lock

* re-add SortableQuoteWithAddress

* add guard function for ExportBitcoinWalletResponseExt ("wallet_descriptor")

* fix remaining linter errors

* remove duplicate XMR

* fix hasUnusualAmountOfTimePassed in SwapStatusAlert.tsx

src-gui/src/renderer/components/pages/help/ConversationsBox.tsx

@@ -378,10 +378,6 @@ function MessageBubble({ message }: { message: Message }) {
       <Box
         sx={(theme) => ({
           padding: 1.5,
-          borderRadius:
-            typeof theme.shape.borderRadius === "number"
-              ? theme.shape.borderRadius * 2
-              : 8,
           maxWidth: "75%",
           wordBreak: "break-word",
           boxShadow: theme.shadows[1],