add a few modules i used to test tail-call of host functions manually

```
spacetanuki% ../../b/toywasm --wasi --print-stats tail.wasm
hello
=== execution statistics ===
operand stack 4 (16 bytes)
locals 4 (16 bytes)
labels 0 (0 bytes)
frames 2 (64 bytes)
                   call            3
              host_call            2
              tail_call            1
         host_tail_call            1
                 branch            0
       branch_goto_else            0
        jump_cache2_hit            0
         jump_cache_hit            0
      jump_table_search            0
type_annotation_lookup1            0
type_annotation_lookup2            0
type_annotation_lookup3            0
spacetanuki% ../../b/toywasm --wasi --print-stats nontail.wasm
hello
=== execution statistics ===
operand stack 4 (16 bytes)
locals 4 (16 bytes)
labels 0 (0 bytes)
frames 2 (64 bytes)
                   call            3
              host_call            2
              tail_call            0
         host_tail_call            0
                 branch            0
       branch_goto_else            0
        jump_cache2_hit            0
         jump_cache_hit            0
      jump_table_search            0
type_annotation_lookup1            0
type_annotation_lookup2            0
type_annotation_lookup3            0
spacetanuki%
```

wat/wasi/nontail.wat

@@ -0,0 +1,28 @@
+;; print hello
+
+(module
+  (func $fd_write (import "wasi_snapshot_preview1" "fd_write") (param i32 i32 i32 i32) (result i32))
+  (func $proc_exit (import "wasi_snapshot_preview1" "proc_exit") (param i32))
+  (func $call_fd_write (param i32 i32 i32 i32) (result i32)
+    local.get 0
+    local.get 1
+    local.get 2
+    local.get 3
+    call $fd_write
+  )
+  (func (export "_start")
+    i32.const 1
+    i32.const 0
+    i32.const 1
+    i32.const 0
+    call $call_fd_write
+    i32.const 0
+    i32.ne
+    call $proc_exit
+  )
+  (memory (export "memory") 1)
+
+  ;; iov_base = 0x100, iov_len = 6
+  (data (i32.const 0) "\00\01\00\00\06\00\00\00")
+  (data (i32.const 0x100) "hello\n")
+)

wat/wasi/tail.wat

@@ -0,0 +1,28 @@
+;; print hello
+
+(module
+  (func $fd_write (import "wasi_snapshot_preview1" "fd_write") (param i32 i32 i32 i32) (result i32))
+  (func $proc_exit (import "wasi_snapshot_preview1" "proc_exit") (param i32))
+  (func $call_fd_write (param i32 i32 i32 i32) (result i32)
+    local.get 0
+    local.get 1
+    local.get 2
+    local.get 3
+    return_call $fd_write
+  )
+  (func (export "_start")
+    i32.const 1
+    i32.const 0
+    i32.const 1
+    i32.const 0
+    call $call_fd_write
+    i32.const 0
+    i32.ne
+    call $proc_exit
+  )
+  (memory (export "memory") 1)
+
+  ;; iov_base = 0x100, iov_len = 6
+  (data (i32.const 0) "\00\01\00\00\06\00\00\00")
+  (data (i32.const 0x100) "hello\n")
+)