feat(GlBreadcrumb): Add boolean prop to disable auto-resize

What does this MR do?

Adds a new autoResize prop to GlBreadcrumb. It keeps the current behavior as default (true).

When set to false, the breadcrumbs component wont try to resize itself to fit into the available space. While this is desired in most of cases and hence the default, we have a use-case where we need a GlBreadcrumb that isn't that "smart" but just simply renders out all its items.

What else does this MR do?

This MR comes with two additional fixes for issues I discovered while migrating existing breadcrumbs in GitLab to this component:

• Switch from window.resize event listener to a ResizeObserver.
• Fix in the calculation of required width.

See the commit messages for details.

Screenshots or screen recordings

recording_1713446431

Integration merge requests

No integration work required as the default behavior wasn't changed.

Does this MR meet the acceptance criteria?

This checklist encourages the authors, reviewers, and maintainers of merge requests (MRs) to confirm changes were analyzed for conformity with the project's guidelines, security and accessibility.

Toggle the acceptance checklist

Conformity

• Code review guidelines.
• GitLab UI's contributing guidelines.
• If it changes a Pajamas-compliant component's look & feel, the MR has been reviewed by a UX designer.
• If it changes GitLab UI's documentation guidelines, the MR has been reviewed by a Technical Writer.
• If the MR changes a component's API, integration MR(s) have been opened (see integration merge requests above).
• Added the ~"component:*" label(s) if applicable.

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• Security reports checked/validated by a reviewer from the AppSec team

Accessibility

If this MR adds or modifies a component, take a few moments to review the following:

• All actions and functionality can be done with a keyboard.
• Links, buttons, and controls have a visible focus state.
• All content is presented in text or with a text equivalent. For example, alt text for SVG, or aria-label for icons that have meaning or perform actions.
• Changes in a component’s state are announced by a screen reader. For example, changing aria-expanded="false" to aria-expanded="true" when an accordion is expanded.
• Color combinations have sufficient contrast.