test: Update test splitting to support new test workflows (#35905)

## **Description**

The script responsible for determining how to split up tests in a given
workflow was failing when I tried to add a new workflow. It didn't seem
to handle the case where a workflow had zero past runs.

It has been updated to use a naive fallback splitting algorithm in this
case.

[![Open in GitHub
Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/MetaMask/metamask-extension/pull/35905?quickstart=1)

## **Changelog**

CHANGELOG entry: null

## **Related issues**

This fixes a CI bug encountered on #31435

## **Manual testing steps**

See this PR for an example of the failures:
#35906

See here for a rebased version of that PR on this branch, which works:
#35913

## **Screenshots/Recordings**

N/A

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

---------

Co-authored-by: Howard Braham <howrad@gmail.com>

Author: Gudahtt

.github/scripts/split-tests-by-timings.ts

@@ -10,7 +10,7 @@ import {
 // Quality Gate Retries
 const RETRIES_FOR_NEW_OR_CHANGED_TESTS = 4;
 
-function readTestResults(TEST_RESULTS_PATH: string): TestRun | undefined {
+function readTestResults(TEST_RESULTS_PATH: string): TestRun {
   const testSuiteName =
     process.env.TEST_SUITE_NAME || 'test-e2e-chrome-browserify';
 
@@ -19,9 +19,12 @@ function readTestResults(TEST_RESULTS_PATH: string): TestRun | undefined {
       readFileSync(TEST_RESULTS_PATH, 'utf8'),
     );
 
-    const testRun: TestRun | undefined = testRuns.find(
+    const testRun: TestRun = testRuns.find(
       (run) => run.name === testSuiteName,
-    );
+    ) || { // If the TestRun is not found, return a dummy object to do the naïve split
+      name: testSuiteName,
+      testFiles: [],
+    };
 
     return testRun;
   } catch (error) {
@@ -82,31 +85,22 @@ export function splitTestsByTimings(
     TEST_RESULTS_FILE = `test/test-results/test-runs-${process.env.SELENIUM_BROWSER}.json`,
   } = process.env;
 
-  try {
-    const testRunLastTime = readTestResults(TEST_RESULTS_FILE);
-
-    if (testRunLastTime) {
-      let testRunNew: TestRun = { name: testRunLastTime.name, testFiles: [] };
+  const testRunLastTime = readTestResults(TEST_RESULTS_FILE);
+  let testRunNew: TestRun = { name: testRunLastTime.name, testFiles: [] };
 
-      testList.forEach((path) => {
-        const testFileLastTime = testRunLastTime.testFiles.find(
-          (file) => file.path === path,
-        );
-
-        if (testFileLastTime) {
-          testRunNew.testFiles.push(testFileLastTime);
-        } else {
-          testRunNew.testFiles.push(getNewBlankTestFile(path));
-        }
-      });
+  testList.forEach((path) => {
+    const testFileLastTime = testRunLastTime.testFiles.find(
+      (file) => file.path === path,
+    );
 
-      return splitTests(testRunNew, changedOrNewTests, totalChunks);
+    if (testFileLastTime) {
+      testRunNew.testFiles.push(testFileLastTime);
+    } else {
+      testRunNew.testFiles.push(getNewBlankTestFile(path));
     }
-  } catch (error) {
-    console.trace(error);
-  }
+  });
 
-  return [];
+  return splitTests(testRunNew, changedOrNewTests, totalChunks);
 }
 
 /**