[browser][MT] Jiterpreter does not know which features are enabled on worker threads

[kg]

The jiterpreter relies on runtimeHelpers properties like featureWasmSimd to determine which features are available, but right now we only populate runtimeHelpers on the main thread. The result is that in an MT build if the jiterpreter is enabled, the traces on worker threads are compiled incorrectly and don't match the ones on the main thread.

The necessary fix for this is to propagate information from the main thread to workers when they are created.

cc @pavelsavara

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