Adds namespace fix for nested sequence and adds support for nested types in Sequence and Scalar ADT

[desaikd]

Description of changes:

This PR fixes namespace for nested sequence types and adds support for nested types in sequence and scalar templates.

List of changes:

• Modified util_macros.templ to use fully-qualified_type_name
• Modified fully_qualified_type_ref method to return FullyQualifiedTypeReference
  • Previously this returned Option<FullyQualifiedTypeReference>
• Modifies add_namespace and reset_namespace
  • Adds check for last value to verify if its module or type name
  • Adds check for empty namespace
• Modifies generator for sequence type namespace
  • Sequence ADT does not use separate class for nested sequences.Hence, modifies the namespace for this in build_sequence_from_constraints.
• Modified templates for nested types in sequence and scalar

Test:

Adds a new test case sequence_with_enum_element this verified both sequence namespace bugfix and support for nested types in sequence.

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.