C++: Do not limit second level scopes to the top-level

[jketema]

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[jketema]

DCA shows some lost results (I'll update as I go through them):

• curl__curl cpp/path-injection
  Lost results flow out via global here: https://github.com/curl/curl/blob/7e814c8717939393d4436d75f5f0c3ffa98c8c53/src/tool_getparam.c#L2900
• erlang__otp cpp/use-after-free
  Lost results flow out of assign here https://github.com/erlang/otp/blob/12509834ed59004b2add47e12806aaaaa43834b8/erts/emulator/asmjit/core/virtmem.cpp#L342
  It does seem like the lost result is an FP
• git-linux cpp/uncontrolled-allocation-size
  Lost result flows out of the first argument of strbuf_read here https://github.com/git/git/blob/041f5ea1cf987a4068ef5f39ba0a09be85952064/apply.c#L413
• git-linux cpp/path-injection
  Lost result flows out of strbuf_add_absolute_path here https://github.com/git/git/blob/041f5ea1cf987a4068ef5f39ba0a09be85952064/tempfile.c#L137
• ImageMagick-ImageMagick cpp/path-injection
  Lost results flow out of AddValueToSplayTree (see https://github.com/ImageMagick/ImageMagick/blob/21db2a08eebf2d13a0af158eae1403b8ebcd73de/MagickCore/splay-tree.c#L154)
• microsoft__CCF cpp/path-injection
• neovim__neovim cpp/uncontrolled-allocation-size
• neovim__neovim cpp/unbounded-write
• nlohmann__json cpp/path-injection
• openjdk-jdk cpp/uncontrolled-allocation-size
• openttd__openttd cpp/path-injection
• systemd-linux cpp/system-data-exposure
• vim__vim cpp/unbounded-write