Fix(CLI/Core): Improvements on the Content Type resource to remove the complete dependency on ids

[jgambarios]

On this PR, we have multiple changes:

1. Improvements on postman tests
2. Better error handling when saving fields without the required data.
3. Modified the FieldFactory to include logic that does not allow modifying the variable name.
4. Small refactors requested by sonarlint to reduce the complexity of some methods.
5. Fixed issue identifying what fields need to be deleted.
6. Improving Content type resource using the idOrVar path param, ignored until now, and also added better error handling related to that parameter.

Refs: #28264

This PR fixes: #28264

[dotcms-sonarqube[bot]]

Quality Gate passed

Issues
0 New issues
16 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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