[k6] Add JVM warmup phase (#2)

[k6] Add JVM warmup phase (#2)

To account for JVM warmup effect, the k6 test suite is run twice:
initially, the whole test suite is run without recording results.

- Added environment variables to allow setting total CM-handles and
  batch size for registration. By reducing total CM-handles during
  warm-up, many more operations will be run.

Issue-ID: CPS-2264
Signed-off-by: danielhanrahan <daniel.hanrahan@est.tech>
Change-Id: Ib1d1e76d31719d788a3e026797faa0a425b320a2