[core] fix(KeyComboTag): use static icon imports

[michael-yx-wu]

Related to #6249

Checklist

• Includes tests (n/a)
• Update documentation (n/a)

Changes proposed in this pull request:

This component previously passed icon string names to a child Icon
component, preventing tree shaking of unused icons. Passing statically
imported icons from @blueprintjs/icons fixes this problem.

Related to #6249.

Reviewers should focus on:

• Verify combo tag icons are rendered at the correct size. (Statically imported icons have a default size of 16, which I think is the correct default?)
• I noticed that the arrow up/down/left/right icons don't render in either version of the combo tester. I didn't try to address that here.
• Perhaps there is a slight regression due to this open issue (Icon edges cut (by transforms?) #6329 (comment)) but since none of these icons are round, it's not very noticeable at all

Screenshot

New:

Old:

[adidahiya]

Use static icon imports for KeyComboTag icon

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.

[adidahiya]

thanks @michael-yx-wu!