Accessibility: Update FilteredConnection to support better usage of labels

Created by: umpox

Description

We typically rely on the placeholder for accessible labels in a lot of places, e.g.:

For further reading, see placeholders are not accessible. Tl;dr - placeholders aren't accessible to screen readers and are only useful before the user has entered text

Note We likely want this to enforce this for all <Input /> elements. There's not a clear solution here yet (as there's so many ways to label an element). The simplest solution is to always enforce that we have some label on these elements, issue here for that: https://github.com/sourcegraph/sourcegraph/issues/36645

Test plan

Tested locally with a screen reader

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.

closes https://github.com/sourcegraph/sourcegraph/issues/35463 closes https://github.com/sourcegraph/sourcegraph/issues/35468