[wasm] Refactor encoder.h to use a proper buffer and remove OldFunctions section.

src/wasm/leb-helper.h

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_LEB_HELPER_H_
 #define V8_WASM_LEB_HELPER_H_
 
 namespace v8 {
 namespace internal {
 namespace wasm {
 
+static const size_t kPaddedVarInt32Size = 5;
+static const size_t kMaxVarInt32Size = 5;
+
 class LEBHelper {
  public:
   // Write a 32-bit unsigned LEB to {dest}, updating {dest} to point after
   // the last uint8_t written. No safety checks.
   static void write_u32v(uint8_t** dest, uint32_t val) {
     while (val >= 0x80) {
       *((*dest)++) = static_cast<uint8_t>(0x80 | (val & 0x7F));
       val >>= 7;
     }
     *((*dest)++) = static_cast<uint8_t>(val & 0x7F);
@@ skipping 100 matching lines @@
     }
     return size;
   }
 };
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_LEB_HELPER_H_