BridgeJS: Enable struct as default parameter and enable default parameters in struct init / methods

[krodak]

Introduction

This PR extends support for default parameter values when exporting Swift functions and constructors to JavaScript/TypeScript using the BridgeJS plugin.

It adds ability to:

• use struct as default parameter
• use default parameters in struct init and methods

Additional Changes

Some minor refactor to DefaultValueGenerator was needed, it got refactored into DefaultValueUtils, moved outside of BridgeJSLink as it needs to be used in JSGlueGen.
I considered moving it to separate module, considered using BridgeJSUtilities too, but it would require dependency on BridgeJSSkeleton so probably not worth it.
I think I might eventually extract some StackBasedThunkBuilder after array implementation to extract some helper functionality and lowering / lifting from JSGlueGen for stack-based types, but let's see after Array implementation 😅
Hope this is ok enough for now, but I'm happy to extract this into separate file, module or use different approach.