• What does your PR fix?

  This is the less controversial part of [vcpkg] Controlling top-level find_package #27950: Tracing find_package.

  With complex projects such as gdal, it is really difficult to see all calls to find_package and to understand side effects of CMAKE_DISABLE_FIND_PACKAGE_<Pkg>. Output gives no indication of top-level calls vs. nesting (find_dependency), and there is no output at all if QUIET is used.

  This PR adds optional tracing output whenever find_package is called, indicating nested calls with indentation.
  It is off by default in order to not change behaviour in user projects, but it could be generally turned on in vcpkg_cmake_configure for maintainer convenience.

Example:

-- find_package(CryptoPP )
-- find_package(PROJ 9 CONFIG QUIET)
--   find_package(unofficial-sqlite3 CONFIG QUIET REQUIRED)
--     find_package(Threads QUIET REQUIRED)
--   find_package(TIFF QUIET REQUIRED)
--     find_package(LibLZMA REQUIRED QUIET)
--       find_package(Threads )
--     find_package(JPEG REQUIRED QUIET)
--     find_package(ZLIB REQUIRED QUIET)
--   find_package(CURL QUIET REQUIRED)
--     find_package(OpenSSL 3 QUIET REQUIRED)
--       find_package(PkgConfig QUIET)
--       find_package(Threads )
--       find_package(Threads REQUIRED)
--     find_package(ZLIB 1 QUIET REQUIRED)
-- find_package(ZSTD NAMES zstd)