Improve workflow editor forms and sidebar

[vinicvaz]

The UI for the workflows editor is not so user-friendly.
There are two points we can start improving:

1. Pieces repositories sidebar (image 2): The sidebar is too compressed, affecting the user experience when browsing repositories and pieces. Expanding its width, considering it's collapsible, would enhance usability.

2. Pieces forms (image 2): Currently, the forms occupy only around 20% of the screen, which is not so good. Increasing it to at least 30% would be beneficial. Additionally, optimizing the item distribution within the forms, such as making upstream checkboxes more compact, would improve usability.

Any other suggestions are welcome!
@tdari @luiztauffer @nathan-vm fyi

Image 1

Image 2