[SG-39362] Extract bootstrap style import @import 'bootstrap/scss/buttons' in client/vscode

Created by: gitstart-sourcegraph

Description

We depend on Bootstrap styles in our global styles a lot. But we don't plan to move forward with Bootstrap because we're working on our design system called Wildcard. To ease the transition to our styles and gain more control over visual changes, we want to move Bootstrap styles that we need into our codebase and eventually drop Bootstrap dependency.

Ref

Parent Issue SourceGraph Issue GitStart Issue

Success criteria

1. All use cases of btn-* are migrated to use wildcard's Button component.

Implementation details

1. Remove bootstrap import @import 'bootstrap/scss/buttons' in forkedBranded.scss.
2. Covert use cases of btn-* className to Button wildcard component.
3. If step 2. above is not doable, let's copy style rule from bootstrap to be used internally.

Test plan

1. Use this guide to run the SourceGraph vscode locally.
2. Compare all use cases of button on the production version of SourceGraph vscode extension which is the instance running on the first vscode window and the local version of SourceGraph vscode extension which the instance that opened up after following the guide. Ensure that there are no UI Changes NOTE: Best to test against the local vscode instance on the main branch since some changes have been pushed to production yet.

App preview:

• Web
• Storybook

Check out the client app preview documentation to learn more.