[Test] Use local devfile.yaml for workspace creation in load-test script

[SkorikSergey]

What does this PR do?

Use local devfile.yaml for workspace creation in load-test script. Start workspaces in parallel.

Logs

Clean up the environment
rm: cannot remove 'dw*': No such file or directory
devworkspace.workspace.devfile.io/dw1 created
devworkspace.workspace.devfile.io/dw1 condition met
Wait for all workspaces are started and calculate average workspaces starting time
Devworkspace dw1 starting time: 36 seconds
==================== Test results ====================
Average workspace starting time for 1 workspaces from 1 started: 36 seconds
0 workspaces failed. See failed workspace pod logs in the current folder for details.
Clean up the environment

What issues does this PR fix or reference?

https://issues.redhat.com/browse/CRW-5633

How to test this PR?

1. Log in to Openshift cluster with DevSpaces deployed from terminal
2. Start load-test.sh script from test/e2e/performance/load-tests. Set number of started workspaces by -c parameter(like./load-test.sh -c 5).
3. As results there are average time of workspace starting and number of failed workspaces.

PR Checklist

As the author of this Pull Request I made sure that:

• The Eclipse Contributor Agreement is valid
• Code produced is complete
• Code builds without errors
• Tests are covering the bugfix or new feature
• The repository devfile is up to date and works
• Sections What issues does this PR fix or reference and How to test this PR completed
• Relevant user documentation updated
• Relevant contributing documentation updated
• CI/CD changes implemented, documented and communicated

Reviewers

Reviewers, please comment how you tested the PR when approving it.