Create new ButtonMultiAction.vue component

[rak-phillip]

Summary

This creates a new button component, ButtonMultiAction.vue, and replaces two targeted instances to address styling issues with Projects/Namespaces.

There are other instances that can be replaced, but they have been left untouched to limit the scope of this change.

Fixes #12007

Occurred changes and/or fixed issues

• Create new component, ButtonMultiAction.vue
• Replace in-table multi action button
• Replace in-table multi action button in shell/components/ExplorerProjectsNamespaces.vue

Technical notes summary

While investigating the issue, it became clear that there is a difference between how scoped styles are applied to slot content in Vue3 when compared to previous versions of Vue. Looking at the similarities between the two implementations told me that a component could be created.

An alternative approach would be to duplicate the class in shell/components/ExplorerProjectsNamespaces.vue.

Relying on unscoped styles is another option, but I prefer the component-driven approach.

Areas or cases that should be tested

• Projects/Namespaces
• Sortable Table

Areas which could experience regressions

• Projects/Namespaces
• Sortable Table

Screenshot/Video

This PR

v2.9

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[cnotv]

Thanks for the initiative to pick the issue up and use the composition API connotation 🥇
I added a comment but it's intended in a conversational manner, not a blocker.

LGTM