Builtin: Redo serialize.lua (minetest#11427)

Features:

* Support for arbitrary references, including self-referencing
* Short output, references "long" strings as a bonus
* Around the same speed, potentially slower if long, short keys are present
* Properly works with NaN and inf

.github/workflows/lua.yml

@@ -19,34 +19,43 @@ jobs:
  name: "Compile and run multiplayer tests"
  runs-on: ubuntu-20.04
  steps:
-  - uses: actions/checkout@v3
-  - name: Install deps
-  run: |
-  source ./util/ci/common.sh
-  install_linux_deps clang-10 gdb libluajit-5.1-dev
-
-  - name: Build
-  run: |
-  ./util/ci/build.sh
-  env:
-  CC: clang-10
-  CXX: clang++-10
-  CMAKE_FLAGS: "-DENABLE_GETTEXT=0 -DBUILD_SERVER=0"
-
-  - name: Integration test + devtest
-  run: |
-  ./util/test_multiplayer.sh
+ - uses: actions/checkout@v3
+ - name: Install deps
+ run: |
+ source ./util/ci/common.sh
+ install_linux_deps clang-10 gdb libluajit-5.1-dev
+
+ - name: Build
+ run: |
+ ./util/ci/build.sh
+ env:
+ CC: clang-10
+ CXX: clang++-10
+ CMAKE_FLAGS: "-DENABLE_GETTEXT=0 -DBUILD_SERVER=0"
+
+ - name: Integration test + devtest
+ run: |
+ ./util/test_multiplayer.sh
 
  luacheck:
  name: "Builtin Luacheck and Unit Tests"
  runs-on: ubuntu-20.04
+
  steps:
+
  - uses: actions/checkout@v3
  - uses: leafo/gh-actions-lua@v9
  with:
  luaVersion: "5.1.5"
  - uses: leafo/gh-actions-luarocks@v4
 
+ - name: Install LuaJIT
+ run: |
+ cd $HOME
+ git clone https://github.com/LuaJIT/LuaJIT/
+ cd LuaJIT
+ make -j$(nproc)
+
  - name: Install luarocks tools
  run: |
  luarocks install --local luacheck
@@ -56,6 +65,7 @@ jobs:
  run: |
  $HOME/.luarocks/bin/luacheck builtin
  $HOME/.luarocks/bin/busted builtin
+ $HOME/.luarocks/bin/busted builtin --lua=$HOME/LuaJIT/src/luajit
 
  - name: Run checks (devtest)
  run: |