Truncation support in Breadcrumb component

As described in https://design.gitlab.com/components/breadcrumb/#truncation, we need to support truncation feature in Breadcrumb component.

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The following discussion from !1869 (merged) should be addressed:

• @tnir started a discussion: (+1 comment)

  Is generic four-item breadcrumb like that?

  For example, at https://gitlab.com/gitlab-org/security-products/analyzers/common, we can see as follows: