Add a test case for unwind with saved FPRs on Windows.

This commit adds a simple test case that reproduces the problem in

tests/wasm/exit_with_saved_fprs.wat

@@ -0,0 +1,40 @@
+;;; This is a test case for https://github.com/bytecodealliance/wasmtime/issues/1967 
+(module
+    (type (func (param i32)))
+    
+    (import "wasi_snapshot_preview1" "proc_exit" (func (type 0)))
+    
+    (func $exit (param i32)
+        local.get 0
+        call 0
+        unreachable
+    )
+    
+    (func $do_something (param f64 f64 f64 f64 f64 f64 f64 f64)
+        i32.const 0
+        call $exit
+        unreachable
+    )
+    
+    (func $has_saved_fprs (export "_start")
+        (local f64 f64 f64 f64 f64 f64 f64 f64)
+        (local.set 0 (f64.const 1))
+        (local.set 1 (f64.const 2))
+        (local.set 2 (f64.const 3))
+        (local.set 3 (f64.const 4))
+        (local.set 4 (f64.const 5))
+        (local.set 5 (f64.const 6))
+        (local.set 6 (f64.const 7))
+        (local.set 7 (f64.const 8))
+        local.get 0
+        local.get 1
+        local.get 2
+        local.get 3
+        local.get 4
+        local.get 5
+        local.get 6
+        local.get 7
+        call $do_something
+        unreachable
+    )
+)