Update FilterBuilder UI according to UX team's new specs (backport #1059)

[mergify[bot]]

Changes

Updated FilterBuilder UI with the following changes:

• made the logical operator always visible
  • set width to 128 px
• made the add button on each rule always visible (previously was only shown on last rule)
  • also made the button the default style with border rather than borderless
  • separated the add and delete button where the add button is left-aligned and the delete is right-aligned
• removed borders around each rule to prevent too many horizontal lines

These changes are based on the UX specifications created by Dan Abney here.

Testing

Tested with the presentation test app: Before:

After:

Note: the removal of the borders/adjustment of spacing may require CSS changes in the InstanceFilterDialog component

---

This is an automatic backport of pull request #1059 done by Mergify.

[mergify[bot]]

Cherry-pick of 0eeaa10787b0612d6364d5427cd2afef835b88cc has failed:

On branch mergify/bp/release/4.17.x/pr-1059
Your branch is up to date with 'origin/release/4.17.x'.

You are currently cherry-picking commit 0eeaa1078.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
    new file:   common/changes/@itwin/components-react/morgan-update-filter-builder-ui_2024-10-01-18-27.json
    modified:   ui/components-react/src/components-react/filter-builder/FilterBuilderRule.scss
    modified:   ui/components-react/src/components-react/filter-builder/FilterBuilderRule.tsx
    modified:   ui/components-react/src/components-react/filter-builder/FilterBuilderRuleGroup.scss
    modified:   ui/components-react/src/components-react/filter-builder/FilterBuilderRuleGroup.tsx
    modified:   ui/components-react/src/components-react/filter-builder/FilterBuilderToolbar.tsx
    modified:   ui/components-react/src/test/filter-builder/FilterBuilderRuleGroup.test.tsx

Unmerged paths:
  (use "git add <file>..." to mark resolution)
    both modified:   docs/changehistory/NextVersion.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally