Update findinmap resolv to handle Ref psedueparams

[kddejong]

Issue #, if available:
fix #3784

Description of changes:

• This will update the FindInMap resolver to look for a secondary key to match a string when the top level key is a Ref to a pseudo-parameter (AWS::AccountId or AWS::Region)
• We will return 0 results if the top level key is a Ref to a pseudo parameter and the second level is also a Ref
• Return a resolution failure if the top level key is a ref to a pseudo parameter and the second level key cannot be found in in the mapping
• Return a resolution failure if the top level key is a ref to a pseudo parameter (AWS::AccountId or AWS::Region) and none of the keys match an accound ID regex or region name.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.78%. Comparing base (a6eb97a) to head (b34d5c0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3785   +/-   ##
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  Coverage   93.78%   93.78%           
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  Files         363      363           
  Lines       12394    12414   +20     
  Branches     2530     2541   +11     
=======================================
+ Hits        11624    11643   +19     
  Misses        429      429           
- Partials      341      342    +1     

Flag	Coverage Δ
unittests	93.74% <100.00%> (+<0.01%)	⬆️

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