wasmtime: Add a config knob to control the maximum number of stack frames captured in a backtrace

Would make capturing a backtrace go from `O(n)` where `n` is the number of Wasm frames on the stack to constant time for some user-defined acceptable constant. Max frames could be set to zero to disable backtraces completely. Would subsume the current (and deprecated) `Config::wasm_backtrace` method.

Follow up to #5049.