Rename job to step in _ert/forward_model_runner

[berland]

This commit will change almost all occurences of the string job to the correct term step, except for where it is regarded as a potentially breaking change for users.

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'just rapid-tests')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codspeed-hq]

CodSpeed Performance Report

Merging #10013 will improve performances by 11%

_{Comparing berland:job_to_step_in_fm_runner (7fd1825) with main (9f5093a)}

Summary

⚡ 1 improvements
✅ 24 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	test_direct_dark_performance_with_storage[gen_x: 20, sum_x: 20 reals: 10-summary-get_record_observations]	1.5 ms	1.4 ms	+11%