use the packaged libsimde-dev

• debian/patches:
  • Use the SIMD Everywhere headers from libsimde-dev, instead of upstream's code copy
• debian/control
  • Build-dep on libsimde-dev
  • Add "Built-Using: ${simde:Built-Using}" to libobs0 & obs-plugins to document the version of libsimde-dev used, as required to keep that version in the Debian archive, which is needed to fulfill the GPL
• debian/copyright:
  • exclude libobs/util/simde/* as we will use the files from libsimde-dev
• debian/rules:
  • Include the recommended flags for SIMDe, especially important for non-X86 architectures