[browser] Unit tests for generated code in JSInterop

[maraf]

Check that each argument, exception and return value is marshalled max once and only when appropriate

• Arguments should be unmarshalled always
• Exception should be marshalled only if exception is raised
• Return value should be marshalled only if exception didn't occur

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Issue Details

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Check that each argument, exception and return value is marshalled max once and only when appropriate

• Arguments should be unmarshalled always
• Exception should be marshalled only if exception is raised
• Return value should be marshalled only if exception didn't occur

Author:	maraf
Assignees:	-
Labels:	arch-wasm, test-enhancement, area-System.Runtime.InteropServices.JavaScript, os-browser
Milestone:	9.0.0

[maraf]

We could use mock library to mock marshalling classes and check what was called