Rework load file script for using devfile samples from local resources

[musienko-maxim]

What does this PR do?

Improve the existing load script:

• Split some of the code fragments on the functions for better readability and maintenance
• Add the possibility of creating the DevWorkSpaces using samples from a file system
• Add additional verification for setting params - when user can enter symbols instead of numbers of workspaces

Screenshot/screencast of this PR

./load-test.sh -c 4
Parameter -c was set to  4 .
Context "load-tests/api-ocp413-mmusiien-crw-qe-com:6443/admin" modified.
Clean up the environment
devworkspacetemplate.workspace.devfile.io/che-code-empty created
devworkspace.workspace.devfile.io/dw1 created
devworkspacetemplate.workspace.devfile.io/che-code-empty configured
devworkspace.workspace.devfile.io/dw2 created
devworkspacetemplate.workspace.devfile.io/che-code-empty configured
devworkspace.workspace.devfile.io/dw3 created
devworkspacetemplate.workspace.devfile.io/che-code-empty configured
devworkspace.workspace.devfile.io/dw4 created
Wait for all workspaces are started and calculate average workspaces starting time
devworkspace.workspace.devfile.io/dw1 condition met
Devworkspace dw1 starting time: 16 seconds
devworkspace.workspace.devfile.io/dw2 condition met
Devworkspace dw2 starting time: 13 seconds
devworkspace.workspace.devfile.io/dw3 condition met
Devworkspace dw3 starting time: 11 seconds
devworkspace.workspace.devfile.io/dw4 condition met
Devworkspace dw4 starting time: 9 seconds
==================== Test results ====================
Average workspace starting time for 4 workspaces from 4 started: 12 seconds
0 workspaces failed. See failed workspace pod logs in the current folder for details.
[mmusiien@fedora load-tests]$ kubectl delete dw --all
devworkspace.workspace.devfile.io "dw1" deleted
devworkspace.workspace.devfile.io "dw2" deleted
devworkspace.workspace.devfile.io "dw3" deleted
devworkspace.workspace.devfile.io "dw4" deleted

What issues does this PR fix or reference?

#22852

How to test this PR?

just run the ./load-test.sh with desired numbers of worspaces

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.

[musienko-maxim]

So we decided first to merge this PR: #22855.
After - get decoupling on function and additional verification for setting params from this PR and implement in new PR
For avoiding duplications