[2.1.0] Suppress some CMake dev warnings for lower message log levels (#6228)

[jhendersonHDF]

Important

Suppresses developer warnings in config/HDF5Pkgconfig.cmake unless CMake log level is VERBOSE or DEBUG.

• Behavior:
  • Suppresses developer warnings in extract_lib_pkgconfig_info in config/HDF5Pkgconfig.cmake unless CMake log level is VERBOSE or DEBUG.
  • Warnings about generator expressions and multi-config generators are now conditional on show_dev_warnings.
• Implementation:
  • Introduces show_dev_warnings flag based on CMake log level.
  • Applies conditional checks for message(AUTHOR_WARNING) in 8 places, including generator expressions and library name issues.

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