ci/cd: trigger URL checks more, and limit amount

Key changes:

- Run URL checks more frequently on every change.
- Introduce environment variable to randomly select and limit URLs
  tested, this way the tests will provide quicker feedback on code
  changes.

Other supporting changes:

- Log more information about test before running the test to enable
  easier troubleshooting.
- Move shuffle function for arrays for reusability and missing tests.

tests/checks/external-urls/TestExecutionDetailsLogger.ts

@@ -0,0 +1,26 @@
+import { indentText } from '@tests/shared/Text';
+
+export class TestExecutionDetailsLogger {
+  public logTestSectionStartDelimiter(): void {
+    this.logSectionDelimiterLine();
+  }
+
+  public logTestSectionEndDelimiter(): void {
+    this.logSectionDelimiterLine();
+  }
+
+  public logLabeledInformation(
+    label: string,
+    detailedInformation: string,
+  ): void {
+    console.log([
+      `${label}:`,
+      indentText(detailedInformation),
+    ].join('\n'));
+  }
+
+  private logSectionDelimiterLine(): void {
+    const horizontalLine = '─'.repeat(40);
+    console.log(horizontalLine);
+  }
+}