Migrate New Environments Form to Vue

What does this MR do?

To allow for richer frontend validations and to align better with the pajamas design system, I've migrated the new environments form to vue.

I've decided to do a full migration rather than using parseRailsFormFields because I found out about it too late, although it would have likely been easier.

The form migration is about as bare-bones as possible, no vuex or other state management, and I use the existing internal API for speed.

Next is to port the Edit Environment form, which is happening separately as it might involve a little bit of vuex or other state management. As it is only 2 fields, I suspect it won't, but we will see.

Screenshots or Screencasts (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

For #29006 (closed)