feat: add transaction and span

[vigneshshanmugam]

• part of [Proposal] Crosslinking Synthetics with APM #265
• Helps with reproducing the error detailed here - apm-agent-rum does not set the custom transaction as root apm-agent-rum-js#1169
• Use this test-repo to simulate a Kibana environment - https://github.com/vigneshshanmugam/tailor-apm-demo
• Once you run the tailor server, use this script for simulation of the bug

journey('Synthetics + APM', ({ page }) => {
  step('go to index page', async () => {
    await page.goto('http://localhost:8080/index');
    // make sure RUM request has been successfully sent to APM server
    await page.waitForResponse(response =>
      response.url().includes('/rum/events')
    );
  });

  step('go to unknown page', async () => {
    await page.goto('http://localhost:8080/unknown');
    // make sure RUM request has been successfully sent to APM server
    await page.waitForResponse(response =>
      response.url().includes('/rum/events')
    );
  });
});

[apmmachine]

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• Start Time: 2022-04-01T22:44:25.225+0000

• Duration: 11 min 47 sec

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Test	Results
Failed	0
Passed	14
Skipped	0
Total	14

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[vigneshshanmugam]

Pursing other way of doing the crosslinking #595