Support prefix and suffix row-level parameters when using a 'select' element in a form

[francesco-cattoglio]

Pretty basic change: I needed a select dropdown menu with a prefix instead of a label (for alignment reasons) and I found out that the 'prefix' row-level parameter was ignored.
I copied the necessary code from the input type of control over to the select one, and fixed the indentation.
Tested locally, everything seems to work allright.

[lovasoa]

Great thank you ! Can you add a small test to prevent regressions ?

[francesco-cattoglio]

Will try to add one and report back soon!

[francesco-cattoglio]

I added a test in the tests/sql_test_files/component_rendering folder. I ran cargo test --all-features, it correctly fails on the base branch, it passes with my changes. As you can see I only tested the 'prefix', not the suffix nor the prefix_icon, but I think this is enough.
I added an extra change to the form docs: in the 'select' example I added a cherry as prefix-icon on the 'select the fruit' (example 6), if you want to keep it, it might count as an extra test 😄

[lovasoa]

thank you very much, the fix is in :)

[francesco-cattoglio]

I just realised I added the 'cherry' as prefix_icon in the wrong part of the documentation, it will only appear in the section "In SQLite, the query would look like", it will not be part of the rendered SQL. Oh well, at least the user will know that the prefix can be used 😅