Ability to pass a Permission boundary name via the context on the command line

[DannyBlazejczak]

Issue #, if available:

Description of changes:

One way to resolve the issue with the permission boundary, is to update the cdk.json, and include a permission boundary here on this level. This is well documented and works well.

I have several accounts, some of which use no permission boundary, some have permission boundaries with different names. Hence I want to be able to pass the permission boundary. In this PR is have done this by passing the name as an additional parameter in the context.

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[apmclean]

Thanks very much, would you be able to add something to (at least one) test case to confirm positive (included) and negative (not included) scenarios with the template rendering as desired?

I've never used this capability, but I surmise it will add a permission boundary to any IAM Role entities the subsequent stacks create?