Fix/862 Search form moved outside of the filter form

[faisal-alvi]

Description of the Change

• This PR moves the search form outside of the filter form.
• Earlier hitting the enter key while the cursor is on the page number input field, the search form was being submitted instead of the filter form.

Closes #862

Verification Process

1. Go to the Pull Content screen.
2. Ensure you're on a connection that has multiple pages of results. If not, create at least 2 posts/pages and set Posts per page to 2 in the Screen Options.
3. Manually enter any page other than 1.
4. Hit enter and see the requested page is loaded.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Changelog Entry

Fixed - Manually entering a page number doesn't work on the Pull screen

Credits

Props @faisal-alvi @dkotter

[dkotter]

Looks good, thanks! Tested both Internal and External connections, both with the default post post type and custom post types and all pagination functionality works as expected now.