[WIP] Form elements refactors

[itisAliRH]

(Please replace this header with a description of your pull request. Please include BOTH what you did and why you made the changes. The "why" may simply be citing a relevant Galaxy issue.) (If fixing a bug, please add any relevant error or traceback) (For UI components, it is recommended to include screenshots or screencasts)

How to test the changes?

(Select all options that apply)

• [ ] I've included appropriate automated tests.
• [x] This is a refactoring of components with existing test coverage.
• [ ] Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• [x] I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.