Performance TestSuite: Add module to record perf metrics in the framework

This module should have a way to record the various performance metrics.

Things to be decided:

1. What to record?

• Need to figure out meaningful metrics to be recorded.
• For the first iteration, finding the time taken for a page to be rendered/loaded in a browser is good enough.

2. How to record?

• There are few ways in which this can be achieved. Need to analyse:
  • Can we use (peek)[https://github.com/peek/peek] gem to find out these metrics (we already use it in our dev code - can this be leveraged?)
  • Can we use window.performance.timing to get the required metrics?
  • Is there an in-house tool to do it as part of gitlab-org/quality/team-tasks~3121561 ?

3. How to assert?

• We need to decide on the acceptable threshold values against which the testrun's performance metrics should be asserted.