Improve flattening

[Porges]

1. Flattening needed to visit arrays, maps, etc to match up inner types.
2. Added a panic if we have missed flattening any properties marked flatten: true; improve reporting of panics during code generation process to include package/typename.
3. If types are not modified then keep using the original type. This improves the typenames a bit (Improve generated typenames  #1591).
4. When matching up spec/status types to augment specs with status, ignore any optionality when matching up types. This makes things work properly with the handcrafted schemas where often the required attribute has been forgotten.

[codecov-commenter]

Codecov Report

Merging #1631 (6067348) into master (0338b8d) will increase coverage by 2.48%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #1631      +/-   ##
==========================================
+ Coverage   62.17%   64.65%   +2.48%     
==========================================
  Files         163      203      +40     
  Lines       10739    12696    +1957     
==========================================
+ Hits         6677     8209    +1532     
- Misses       3422     3760     +338     
- Partials      640      727      +87     

Impacted Files	Coverage Δ
hack/generated/controllers/generic_controller.go	70.45% <0.00%> (ø)
hack/generated/main.go	0.00% <ø> (ø)
hack/generated/pkg/armclient/raw_client.go	56.52% <ø> (-2.61%)	⬇️
hack/generated/pkg/armclient/types.go	78.02% <ø> (+4.15%)	⬆️
hack/generated/pkg/genruntime/base_types.go	96.55% <ø> (ø)
hack/generated/pkg/genruntime/errors.go	40.90% <ø> (-36.37%)	⬇️
hack/generated/pkg/genruntime/property_bag.go	80.00% <ø> (ø)
...ck/generated/pkg/genruntime/resolved_references.go	50.00% <ø> (ø)
...ack/generated/pkg/genruntime/resource_reference.go	78.57% <ø> (+28.57%)	⬆️
...ted/pkg/reconcilers/azure_deployment_reconciler.go	66.58% <ø> (+8.36%)	⬆️
... and 253 more

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