Add CorsPolicyBuilder to WebApp/WebHost extensions

[cieciurm]

Description

Hi all,

This PR addresses issue #1251 by adding optional parameter Action<CorsPolicyBuilder> to two extension methods:

• ManagementWebHostBuilderExtensions => AddAllActuators
• ManagementWebApplicationBuilderExtensions => AddAllActuators

Fixes #1251

I'd like to ask for guidance and suggestion about testing this change.
I can see that there aren't many unit tests for those extension methods in general.

My only idea would be to inspect IServiceCollection whether the underlying call to ActuatorServiceCollectionExtensions => AddSteeltoeCors was made.
Kindly please advise if such implementation would be good.

Thanks in advance!

Quality checklist

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[TimHess]

/azp run Steeltoe.All

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[sonarcloud]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[TimHess]

LGTM, thanks!