Further improve user login in tests (Follow up for #3469309)

Problem/Motivation

There are a few things we might want to improve from ✨ Use one-time login link instead of user login form in BrowserTestBase tests Fixed but they're still undecided and it seems we need the follow-up created before we can progress it.

• Use one-time login links for LocaleTranslatedSchemaDefinitionTest
• Use one-time login links for UserTokenReplaceTest
• Consider deprecating the fallback to the user login form
• Provide a generic helper function to load and submit the login form for a user, with optional overrides of Url options (e.g. destination) and form values

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet