Remove control type filed

[DanSava]

Issue
Resolves #9774

Approach
Short description of the approach

(Screenshot of new behavior in GUI if applicable)

• 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 #9901 will improve performances by 10.99%

_{Comparing DanSava:remove-control-type (a6f8457) with main (83ea886)}

Summary

⚡ 1 improvements
✅ 24 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	test_load_from_context[gen_x: 20, sum_x: 20 reals: 10]	6.9 ms	6.3 ms	+10.99%

[verveerpj]

So this case would not be allowed anymore: A control group where most variable names are arbitrary, but one or more happen to be well names?

If so, it seems an arbitrary limitation, somebody may have a case that breaks it.

[DanSava]

Yes, that will no longer be allowed.

We could remove this arbitrary limitation but once the control type filed is removed we can no longer enforce any constraint on the well name and variable names. So as far as I can see there we have the following options:

1. We keep the control type.
2. We remove the control type and this validation
3. We add this arbitrary limitation that might break some cases where there are well_controls and generic_controls that happen to have some of the variable names match the well names.

There could be some other options I am not considering at the moment, but I am open to suggestions.