Enhance SiteDefinition provision - enable provision under the managed path

[SubPointSupport]

SiteDefinition provision should be supported at the root scope under the managed path.

Currently, the following scenarios are supported and covered in the regression tests:

• /my-collection
• /sites/my-collection
• /custom-path/my-collection

The following is to be implemented:

• /custom-path/

Community feedback:
https://www.yammer.com/spmeta2feedback/#/threads/show?threadId=733969996

[SubPointSupport]

Added CanDeploy_Simple_Site_UnderRandomManagedPath_AsRoot test to ensure the mentioned case.
Full set of the tests is under "Regression.Scenarios.Sites"

• CanDeploy_Simple_Site_UnderRandomManagedPath
• CanDeploy_Simple_Site_UnderRandomManagedPath_AsRoot
• CanDeploy_Simple_Site_UnderSitesManagedPath
• CanDeploy_Simple_Site_WithNullableSecondaryContactLogin