fix(parser): type hints should reflect primitive types support (#8175)

* fix: parser type hints should reflect primitive types

As per #4502, primitive types are supported by the `parser` utility. However, the type hints utilized in the functions and envelopes there do not reflect that at the moment, making type checkers lack when inferring the return types, for example. This aims to improve this situation by adjusting the type hints there.

* fix: small changes

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Co-authored-by: Leandro Damascena <lcdama@amazon.pt>