✅(vitest) Make tests run concurrently (#5380)

**Description**

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They used to be running in a concurrent fashion in the past. But we
stopped doing it due to a recent regression on the stability of our CI
with Node 23.

The regression being still noticeable even without it and because of the
cost of not doing the runs in a concurrent fashion, we move back to
concurrent execution.

Regression was not related to vitest, but we dropped concurrent on it
too in the past.

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- [x] Category: ✅ Add or update tests
- [x] Impacts: Faster CI

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packages/vitest/test/vitest-fast-check.spec.ts

@@ -35,7 +35,7 @@ describe.each<DescribeOptions>([
   { specName: 'test', runnerName: 'test' },
   { specName: 'it', runnerName: 'it' },
 ])('$specName', ({ runnerName }) => {
-  it(`should support ${runnerName}.prop`, async () => {
+  it.concurrent(`should support ${runnerName}.prop`, async () => {
     // Arrange
     const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
       runner.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -51,7 +51,7 @@ describe.each<DescribeOptions>([
   });
 
   describe('at depth 1', () => {
-    it(`should support ${runnerName}.concurrent.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.concurrent.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.concurrent.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -66,7 +66,7 @@ describe.each<DescribeOptions>([
       expectPass(out, specFileName);
     });
 
-    it(`should support ${runnerName}.fails.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.fails.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.fails.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -96,7 +96,7 @@ describe.each<DescribeOptions>([
       expectPass(out, specFileName);
     });
 
-    it(`should support ${runnerName}.skip.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.skip.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.skip.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -111,7 +111,7 @@ describe.each<DescribeOptions>([
       expectSkip(out, specFileName);
     });
 
-    it(`should support ${runnerName}.todo.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.todo.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.todo.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -128,7 +128,7 @@ describe.each<DescribeOptions>([
   });
 
   describe('at depth strictly above 1', () => {
-    it(`should support ${runnerName}.concurrent.fails.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.concurrent.fails.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.concurrent.fails.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -143,7 +143,7 @@ describe.each<DescribeOptions>([
       expectFail(out, specFileName);
     });
 
-    it(`should support ${runnerName}.concurrent.fails.only.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.concurrent.fails.only.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.concurrent.fails.only.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -158,7 +158,7 @@ describe.each<DescribeOptions>([
       expectFail(out, specFileName);
     });
 
-    it(`should support ${runnerName}.concurrent.fails.skip.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.concurrent.fails.skip.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.concurrent.fails.skip.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {
@@ -173,7 +173,7 @@ describe.each<DescribeOptions>([
       expectSkip(out, specFileName);
     });
 
-    it(`should support ${runnerName}.concurrent.fails.todo.prop`, async () => {
+    it.concurrent(`should support ${runnerName}.concurrent.fails.todo.prop`, async () => {
       // Arrange
       const { specFileName, vitestConfigRelativePath: jestConfigRelativePath } = await writeToFile(runnerName, () => {
         runner.concurrent.fails.todo.prop([fc.string(), fc.string(), fc.string()])('property', (a, b, c) => {