Remove global header from global settings

### What is this about?

The global header currently appears in our Settings, which is an uncommon pattern. Removing it simplifies users' cognitive load and increases the likelihood of finding the right setting.

### Scenario

When a user wants to make a change in Settings, they navigate to this section. They should not see the header.

### Design

_No response_

### Technical Details

- `multichain-app-header` no longer exists in the global settings
- `padding-left` and `padding-right` updated to `16px`
- `font-size` in `.tab-bar__tab__content__title` updated from `1.125rem` to `1rem`
- `font-weight` in `.tab-bar__tab__content__title` updated from `normal` to `500`
- `8px` `padding` on the right of the `chevron` removed
- Search Bar replaced with the component from the Component API

### Threat Modeling Framework

_No response_

### Acceptance Criteria

[Figma link](https://www.figma.com/design/aMYisczaJyEsYl1TYdcPUL/Portfolio-View?node-id=3479-43470&t=onfs1L939A4x62sk-4)

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

Ping @amandaye0h for context