formula: add jbeder/yaml-cpp

[MeteorsLiu]

Translate the pinned Conan Center yaml-cpp recipe into idiomatic LLAR Formula modules.

Summary:

• Add jbeder/yaml-cpp with exact tags, a complete upstream-tag comparator, CMake build thresholds, relocatable yaml-cpp.pc metadata, and an installed C++ parser/emitter consumer test.
• Preserve shared/fPIC behavior, Linux/FreeBSD libm linkage, static and Windows shared export defines, and the pinned Conan package interface.

Validation:

• llar test passed for yaml-cpp-0.6.3, yaml-cpp-0.7.0, 0.8.0, and yaml-cpp-0.9.0 on the local explicit linux/amd64 matrix.
• llar test passed for static/shared and fPIC option selections, plus a repeated cache-hit consumer test.

Closes #272

[fennoai]

The formula structure, option handling, relocatable pkg-config metadata, and consumer tests are otherwise consistent with the requested LLAR translation. The remaining issue is the unhandled upstream portability patch for the claimed 0.7.x range.

[fennoai]

[P2] Apply the required 0.7.0 libc++ portability patch

fromVer "yaml-cpp-0.6.3" makes this formula serve yaml-cpp 0.7.0 (until the 0.9.0 threshold), but the pinned Conan recipe applies 0002-libcxx-and-gcc.patch specifically for 0.7.0. That upstream patch changes include/yaml-cpp/node/iterator.h and is required for the GCC + libc++ combination; without an equivalent patch or a separate 0.7.0 threshold, selecting this formula for that version can fail to compile on a supported toolchain. Please add the patch behavior or split the range so 0.7.0 is not claimed without it.