Buttons for creating content files in new project should be linked to Web IDE

Problem to solve

As a follow up on https://gitlab.com/gitlab-org/gitlab-ce/issues/45687, it has been decided to split scope of that issue so that linking the "New file", "Add LICENSE", etc buttons in freshly-created project would link to Web IDE. This is part of replacement of the ACE editor process and is a logic next step after

• https://gitlab.com/gitlab-org/gitlab-ce/issues/45687, and
• https://gitlab.com/gitlab-org/gitlab-ce/issues/57668

are implemented.

Further details

The issue is limited to the buttons, shown to user after creating a new project

Proposal

The process should piggybacks https://gitlab.com/gitlab-org/gitlab-ce/issues/57668

What does success look like, and how can we measure that?

Buttons, shown to user in newly-created project should be linked to Web IDE: clicking any of those will create a new file in the project through Web IDE interface

Links / references

Availability and Testing

• Any existing E2E tests using the buttons need to be modified to follow the new flow via Web IDE, please include the SET (@a_mcdonald) to implement it in the same MR(s) as the development.
• Manual job package-and-qa needs to be run before any merge.
• We also have existing test coverage for adding the first file to an empty repository in Web IDE in create_first_file_in_web_ide_spec. The test navigates to Web IDE via URL, this needs to be updated to go through UI ("New file" button), but this can happen async after the merge.