all: format code according to Go 1.19 rules

Go 1.19 started reformatting code in a way that makes it more obvious
how it will be rendered on pkg.go.dev. It gets it almost right, but not
entirely. Therefore, I had to modify some of the comments so that they
are formatted correctly.

src/runtime/gc_conservative.go

@@ -259,6 +259,7 @@ func calculateHeapAddresses() {
 
 // alloc tries to find some free space on the heap, possibly doing a garbage
 // collection cycle if needed. If no space is free, it panics.
+//
 //go:noinline
 func alloc(size uintptr, layout unsafe.Pointer) unsafe.Pointer {
 	if size == 0 {