* sorta working in runtime
* wasmtime-runtime: get rid of wasm-backtrace feature
* wasmtime: factor to make backtraces recording optional. not configurable yet
* get rid of wasm-backtrace features
* trap tests: now a Trap optionally contains backtrace
* eliminate wasm-backtrace feature
* code review fixes
* ci: no more wasm-backtrace feature
* c_api: backtraces always enabled
* config: unwind required by backtraces and ref types
* plumbed
* test that disabling backtraces works
* code review comments
* fuzzing generator: wasm_backtrace is a runtime config now
* doc fix
bffce37050