Support plugging external profilers into the Cranelift timing infrastructure (#5749)

* Remove no-std code for cranelift_codegen::timings

no-std mode isn't supported by Cranelift anymore

* Simplify define_passes macro

* Add egraph opt timings

* Replace the add_to_current api with PassTimes::add

* Omit a couple of unused time measurements

* Reduce divergence between run and run_passes a bit

* Introduce a Profiler trait

This allows plugging in external profilers into the Cranelift profiling
framework.

* Add Pass::description method

* Remove duplicate usage of the compile pass timing

* Rustfmt

cranelift/codegen/src/context.rs

@@ -213,7 +213,6 @@ impl Context {
     ///
     /// Returns information about the function's code and read-only data.
     pub fn compile(&mut self, isa: &dyn TargetIsa) -> CompileResult<&CompiledCode> {
-        let _tt = timing::compile();
         let stencil = self.compile_stencil(isa).map_err(|error| CompileError {
             inner: error,
             func: &self.func,
@@ -379,6 +378,8 @@ impl Context {
 
     /// Run optimizations via the egraph infrastructure.
     pub fn egraph_pass(&mut self) -> CodegenResult<()> {
+        let _tt = timing::egraph();
+
         trace!(
             "About to optimize with egraph phase:\n{}",
             self.func.display()