Change copy of Welcome screen

What does this MR do?

Currently, the welcome screen when signing up, displays the question "Who will be using this GitLab subscription?". This is accurate for users who are signing up after selecting a plan to subscribe to, but not in other cases.

Change the text of that question to "Who will be using this GitLab trial?" when users are signing up for a trial license and to "Who will be using GitLab?" for user signing up in other cases. Also change the CTA button texts and whether the progress bar is visible based on the flow.

Regular flow	Subscription flow	Trial flow

Closes #202632 (closed)