Upsell the GitLab Terraform features - iteration 2

What does this MR do?

This MR is a part of changing the GitLab-managed Terraform state banner. As discussed in that MR we want to split the task to ship the change safely for the mixed deployment scenario

We decided to proceed in 3 steps:

1. Change the design using the old logic - current step
2. Introduce the backend change
3. Then in 14.3 switch to the new implementation using UserCalloutDismisser.

Current MR:

• changes the banner design from introduction to promotion
• adds illustration to make it prominent that the banner is about Terraform
• changes the logic of managing cookie for the banner from per-project to per-user basis

Screenshots or Screencasts (strongly suggested)

Before	After

How to setup and validate locally (strongly suggested)

1. Create a project that contains Terraform files (.tf files should be at least in the top 5 files types)
2. View the banner on the top
3. After dismissing the banner try to reload the page and go to another project that contains Terraform files. Verify that the banner is not shown anymore.

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.

Related to #336360 (closed)