[wasm][coreclr] Extract call helpers to separate source file

[radekdoulik]

And use output of work in progress generator to get more thunks.

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[Copilot]

Pull Request Overview

This PR refactors WASM call helper functions by extracting them from the main helpers.cpp file into a new dedicated callhelpers.cpp source file. The changes include adding support for additional thunk signatures generated by a work-in-progress InterpToNativeGenerator tool.

Key changes:

• Extracted call helper functions and signature-to-thunk mappings to a separate source file
• Added new thunk functions for additional parameter/return type combinations, particularly for float32, float64, and various int32/int64 parameter patterns
• Updated the build system to include the new callhelpers.cpp file

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/coreclr/vm/wasm/helpers.cpp	Removed call helper functions and thunk mapping table; added include for new callhelpers.hpp header
src/coreclr/vm/wasm/callhelpers.hpp	New header file declaring the StringToWasmSigThunk structure and external references to global thunk arrays
src/coreclr/vm/wasm/callhelpers.cpp	New source file containing all call helper function implementations and the thunk mapping table
src/coreclr/vm/CMakeLists.txt	Added callhelpers.cpp to the build configuration for WASM architecture