Feature: Nontrapping Float-to-Int Conversions

[bushidocodes]

• i32.trunc_sat_f32_s
• i32.trunc_sat_f32_u
• i32.trunc_sat_f64_s
• i32.trunc_sat_f64_u
• i64.trunc_sat_f32_s
• i64.trunc_sat_f32_u
• i64.trunc_sat_f64_s
• i64.trunc_sat_f64_u

Also need to verify that the alternative conversion instructions trap as expected

Reference: https://github.com/WebAssembly/nontrapping-float-to-int-conversions/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md