Bump Vitest to v4 (#19216)

This PR bumps Vitest from v2 to v4. As far as I know we don't use any
Vitest specific features in our tests, but had to upgrade the
`vitest.workspace.ts` file to a `vitest.config.ts` file instead.

The only features we use are the typical `describe`, `it`, `test`, and
`expect` functions.

The only other part we use is `vi.spyOn` and `vi.fn` but those didn't
change in API either.

The test shards were removed to prevent errors. Not all suites have
enough files / tests to be broken up into 3 parts so Vitest now errors
when that happens.

### Test plan

1. All tests should pass in CI.
2. All integration tests should pass in CI.

---------

Co-authored-by: Jordan Pittman <jordan@cryptica.me>

integrations/utils.ts

@@ -37,6 +37,7 @@ interface TestConfig {
     [filePath: string]: string | Uint8Array
   }
 
+  timeout?: number
   installDependencies?: boolean
 }
 interface TestContext {
@@ -86,7 +87,7 @@ export function test(
   return defaultTest(
     name,
     {
-      timeout: TEST_TIMEOUT,
+      timeout: config.timeout ?? TEST_TIMEOUT,
       retry: process.env.CI ? 2 : 0,
       only: only || (!process.env.CI && debug),
       skip,