Fix incorrect AbsolutePath in GetContentRoute

[ava3a13]

Fixes #16745

Description

Previous implementation did not correctly decode Uri into the string - e.g. 'bar%20nix' into 'bar nix'
Original proposal was to pass contentRoute.AbsolutePath into the Uri.UnescapeDataString function.
Current solution calls to GetAbsolutePathDecoded provided on the Uri instance via the UriExtensions class - meaning that all the unit tests are covered within UriExtensionsTests.

[github-actions]

Hi there @ava3a13, thank you for this contribution! 👍

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[mikecp]

Hello @ava3a13 ,

Thanks a lot for spotting the issue and providing the fix 👍

One of us from the core collaborators team will have a look at it soon 😁

Cheers!