build: migrate to GitHub Actions (#42720)

* build: migrate to GitHub Actions

* build: use old clang-format binary path

* debug (do not merge): intentionally bust Linux cache

* build: unskip cache creation

script/split-tests.js

@@ -0,0 +1,32 @@
+const fs = require('node:fs');
+const glob = require('glob');
+
+const currentShard = parseInt(process.argv[2], 10);
+const shardCount = parseInt(process.argv[3], 10);
+
+const specFiles = glob.sync('spec/*-spec.ts');
+
+const buckets = [];
+
+for (let i = 0; i < shardCount; i++) {
+  buckets.push([]);
+}
+
+const testsInSpecFile = Object.create(null);
+for (const specFile of specFiles) {
+  const testContent = fs.readFileSync(specFile, 'utf8');
+  testsInSpecFile[specFile] = testContent.split('it(').length;
+}
+
+specFiles.sort((a, b) => {
+  return testsInSpecFile[b] - testsInSpecFile[a];
+});
+
+let shard = 0;
+for (const specFile of specFiles) {
+  buckets[shard].push(specFile);
+  shard++;
+  if (shard === shardCount) shard = 0;
+}
+
+console.log(buckets[currentShard - 1].join(' '));