Add OneTrust to additional sign up pages

What does this MR do and why?

Related to gitlab-com/marketing/digital-experience/buyer-experience#200 (closed) Related to !73324 (merged)

This adds the OneTrust partial to pages in the sign up flow that we missed earlier. Eventually, we'll be adding instrumentation to these pages, and adding OneTrust is a pre-requisite to doing that.

• https://gitlab.com/users/almost_there
• https://gitlab.com/users/sign_up/groups/new
• https://gitlab.com/users/sign_up/projects/new
• https://gitlab.com/users/sign_up/groups_projects/new
• https://gitlab.com/users/sign_up/welcome/trial_getting_started

It also adds the OneTrustCSP concern to the confirmations controller in order for /users/almost_there to work.

Screenshots or screen recordings

These are strongly recommended to assist reviewers and reduce the time to merge your change.

OneTrust available in the JS console on localhost:3000/users/almost_there:

How to set up and validate locally

Validate OneTrust not running

1. In rails console, make sure the feature flag is off

   Feature.disable(:ecomm_instrumentation)

2. Optionally add the one_trust_id config value to your gitlab.yml file

   ## OneTrust
   one_trust_id: '_your_one_trust_id'

3. Visit any of the listed pages above, such as localhost:3000/users/almost_there
4. Check that OneTrust is not installed/invoked. Running OneTrust in the Javascript console to get an undefined error or checking the network requests.

Validate OneTrust running properly

1. In rails console, make sure the feature flag is enabled

   Feature.enable(:ecomm_instrumentation)

2. Add the one_trust_id config value to your gitlab.yml file

   ## OneTrust
   one_trust_id: '7f944245-c5cd-4eed-a90e-dd955adfdd08-test'

3. Visit any of the listed pages above, such as localhost:3000/users/almost_there
4. Check that OneTrust is installed and running. Running OneTrust in the Javascript console to get an object or checking the network requests.

## MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.