homepage search revisions

[gumaerc]

What are the relevant tickets?

Closes https://github.com/mitodl/hq/issues/5298

Description (What does it do?)

This PR addresses some changes to the homepage hero / search area that were not addressed as part of #1454.

Screenshots (if appropriate):

How can this be tested?

• Spin up this branch of mit-learn
• Visit the homepage at http://localhost:8062/
• Verify that the changes from the issue have been addressed:
  • If you type something in the search box, the x button to clear your search should be narrower, but still the whole height of the text box with no hover state
  • The sizing of the search chips below the text box should be properly sized now, have the correct border / background colors and hover states and the correct icons
  • There should now be a drop shadow on the text box

[ChristopherChudzicki]

LGTM

As mentioned in slack, I'm confused by the

We want to increase the size of the "x" that appears when user starts typing.

in the issue... but it seems to match the screenshot there. I can't find the X in figma.