test: fix system locale override (#7317)

Apparently setting `LC_ALL` in `vitest.setup.ts` doesn't work, as this
is after the locale settings are read, but it does work in a
`globalSetup` file.

This can be observed locally with the Workflows tests:
```
➜  wrangler git:(fix-test-locale) npx vitest run src/__tests__/workflows.test.ts >&/dev/null; echo $?
0
➜  wrangler git:(fix-test-locale) git checkout origin/main vitest.config.mts && LC_ALL=en_UK npx vitest run src/__tests__/workflows.test.ts >&/dev/null; echo $?
Updated 1 path from e1554242a
1
```

Author: ns476

packages/wrangler/src/__tests__/vitest.global.ts

@@ -0,0 +1,7 @@
+export function setup(): void {
+	// Set `LC_ALL` to fix the language as English for the messages thrown by Yargs,
+	// and to make any uses of datetimes in snapshots consistent.
+	// This needs to be in a globalSetup script - it won't work in a setupFile script.
+	// https://github.com/vitest-dev/vitest/issues/1575#issuecomment-1439286286
+	process.env.LC_ALL = "C";
+}

packages/wrangler/src/__tests__/vitest.setup.ts

@@ -22,9 +22,6 @@ chalk.level = 0;
 	global as unknown as { __RELATIVE_PACKAGE_PATH__: string }
 ).__RELATIVE_PACKAGE_PATH__ = "..";
 
-// Set `LC_ALL` to fix the language as English for the messages thrown by Yargs.
-process.env.LC_ALL = "en";
-
 vi.mock("ansi-escapes", () => {
 	return {
 		__esModule: true,

packages/wrangler/vitest.config.mts

@@ -65,6 +65,7 @@ export default defineConfig({
 		// eslint-disable-next-line turbo/no-undeclared-env-vars
 		outputFile: process.env.TEST_REPORT_PATH ?? ".e2e-test-report/index.html",
 		setupFiles: path.resolve(__dirname, "src/__tests__/vitest.setup.ts"),
+		globalSetup: path.resolve(__dirname, "src/__tests__/vitest.global.ts"),
 		reporters: ["default", "html"],
 		globals: true,
 		snapshotFormat: {