feat: Added generic Divider and remove el-menu-divider

[kurtdoherty]

Context

• Menu.Divider was originally implemented as a <hr> specific to menus, but this was not meant to be the case.
• There are other use-cases that require a divider that we currently have no generic component for.

This PR

• Effectively renames Menu.Divider to Divider.

note: Menu.Divider is still available for convenience, but is just a re-export of the generic Divider component.
note: The el-menu-divider class is has been removed as a result of the rename.

[rpt-uk-github]

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[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for 90d624d1	✅ 100.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (90d624d)	Report Missing	Report Missing	Report Missing
Head commit (c3376f4)	8305	7669	92.34%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#711)	7	7	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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Footnotes

1. Codacy didn't receive coverage data for the commit, or there was an error processing the received data. Check your integration for errors and validate that your coverage setup is correct. ↩