Support for mutable lambdas in `catch` functions.

[kring]

I noticed while working on CesiumGS/cesium-unreal#1526 that a bug made it impossible (compiler error) to pass a mutable lambda to a catchImmediately or catchInMainThread function. Mutable lambdas are necessary when you want to std::move a captured value elsewhere, because in a non-mutable lambda (the default), all captured parameters are const.

This PR fixes it by adding the missing mutable to the wrapper lambdas.

[j9liu]

Seems good to me, thanks @kring !