capture unhandled exception on tested pages

[vigneshshanmugam]

• we only capture JS errors console error and warnings which are captured via console.error and console.warn.

• Need to capture uncaught exceptions that gets thrown which would be useful for debugging and associate it with each steps.

We can use page.on('pageerror') events - https://playwright.dev/docs/api/class-page/#pageonpageerror

[dominiqueclarke]

Seeing this implemented all the way through to Kibana for Synthetics agent beta.16, when tested against Kibana branch 7.16 and commit 0c347055e667851383a7415dfeaaa985bc01fe07