Implement std::ranges view support in matchers

[ozars]

• Add feature flags for std::ranges and std::views::as_const detection.
• Extend StlContainerView with a std::ranges::view specialization.
• Introduce internal::ValueType to deduce element/value type for both STL containers and ranges, while keeping backward-compatibility for the existing behavior.
• Update container matchers to use internal::ValueType instead of assuming nested value_type.
• Add coverage for common matchers against std::ranges views (e.g. ElementsAre, ElementsAreArray, Contains, Pointwise, UnorderedPointwise, Pointee).
• Resolves support ranges with Container Matchers  #3403.
• Resolves Matchers for C++20 ranges #4512.
• Resolves [FR]: Loosen restrictions on what types are considered containers for matchers #4534.

Tested: On x86_64-pc-linux-gnu, with gcc 15.2.1 and clang 21.1.6, with libstdc++ for both, with build types Debug and Release, with C++ standards 17, 20 and 23.

Ad-hoc test script is given below.

#!/bin/bash

set -o errexit
set -o nounset
set -o pipefail

function check() {
  local cc="$1"
  local cxx="$2"
  local build_type="$3"
  local std="$4"
  local build_dir="build_${cc}_${build_type}_${std}"
  echo -e "\033[1m"
  echo "=== Building with $cc/$cxx, type=$build_type, std=$std ==="
  echo -e "\033[0m"
  rm -rf "$build_dir"
  mkdir -p "$build_dir"
  CC="$cc" CXX="$cxx" \
    cmake \
      -S . \
      -B "$build_dir" \
      -G "Ninja" \
      -Dgtest_build_tests=ON \
      -Dgmock_build_tests=ON \
      -DCMAKE_BUILD_TYPE="$build_type" \
      -DCMAKE_CXX_STANDARD="$std" \
      -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
  cmake --build "$build_dir" -- -j$(nproc)
  cmake --build "$build_dir" --target test
}

check "gcc" "g++" "Debug" "17"
check "gcc" "g++" "Release" "17"
check "gcc" "g++" "Debug" "20"
check "gcc" "g++" "Release" "20"
check "gcc" "g++" "Debug" "23"
check "gcc" "g++" "Release" "23"

check "clang" "clang++" "Debug" "17"
check "clang" "clang++" "Release" "17"
check "clang" "clang++" "Debug" "20"
check "clang" "clang++" "Release" "20"
check "clang" "clang++" "Debug" "23"
check "clang" "clang++" "Release" "23"