Reduce CPU time when initiating RepositoryCacheKeys

[Henr1k80]

Avoid an unneeded lookup in the Keys dictionary, when writing the newly created key.

This will reduce the CPU time spent in the important startup phase, where every cache is empty and everything is undergoing optimization and CPU heavy.

When the all keys have been written, the cost will be the same as before, as there is only lookup, no writing.

Prerequisites

• I have added steps to test this contribution in the description below

[github-actions]

Hi there @Henr1k80, thank you for this contribution! 👍

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[mikecp]

Hello @Henr1k80,

Thanks for this new enhancement 👍
Someone from the team will have a look at it soon.

Cheers!