Reduce execution time of end-to-end tests

[2opremio]

They currently take ~ 20 mins , which is a long time.

We could parallelize them by:

• Running multiple tests in parallel in the same cluster. This causes conflicts between the tests. For instance it would require ensure that the resources created in each test are unique, to avoid clashes.
• Using multiple kubernetes clusters and distributing tests across the clusters, to be run sequentially in each cluster. This may make it harder to run tests in pre-existing clusters (e.g. locally) but I guess we can always add an option to run tests sequentially or use a single cluster.