Deduplicate e2e test hook helpers

[fspv]

Description

There is some duplication in the e2e tests for hooks. This PR moves similar functions to the helpers library so we can reuse them across the tests.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test updates
• CI/CD related changes
• Other (please describe):

Testing

• Added new unit tests
• Added new integration tests
• Ran existing test suite
• Tested manually (please provide steps)

Related Issues

#3406
#3408

Additional Context

Was raised here #3406 and here #3408
The functions in the tests in those PRs will be also deduplicated once they're landed and this PR is rebased on main.

[saku3]

LGTM

Personally, I think the ideal structure is to keep all hook-related tests under the hooks directory.
That way, the tests are grouped by feature, which makes them easier to discover, maintain, and extend as more hook-related cases are added.

e.g.

hooks/
  mod.rs
  helpers.rs
  invoke.rs
  prestart.rs
  create_runtime.rs
  poststart.rs
  poststop.rs

[saku3]

If there are no comments from @utam0k , I’ll merge it this week.