CI: Pass CMAKE_POLICY_VERSION_MINIMUM=3.5 in clang-tidy and clazy

CMake 4.x on the ubuntu-26.04 runners removed compatibility with
cmake_minimum_required(VERSION < 3.5), and ThirdParty/openzgy/zfp declares
VERSION 3.1 (3.4 on Windows), so configuring fails at
ThirdParty/openzgy/zfp/CMakeLists.txt:4.

zfp is a nested submodule of openzgy pinned at 0.5.5; the first release
declaring a 3.5-or-later minimum is 1.0.0, so clearing this properly means a
major-version upgrade of a compression library and whatever API changes that
brings to the openzgy wrapper. That is worth doing on its own schedule, not as
part of a CI fix.

Pass the policy minimum instead, which is already the established approach in
this repository: ResInsightMac.yml passes the same flag, and both
x64-linux-release and x64-windows-release set it via
VCPKG_CMAKE_CONFIGURE_OPTIONS for the same reason.

A scan of every CMakeLists.txt in the repository and its submodules (excluding
ThirdParty/vcpkg/ports, which the triplets already cover) finds zfp to be the
only remaining declaration below 3.5.

ResInsightWithCache.yml is deliberately left alone: it still runs on
ubuntu-24.04, and its cmake command line feeds the buildcache hash, so adding a
flag there would invalidate the cache for no present benefit. It will need the
same flag when it moves to ubuntu-26.04.

.github/workflows/clang-tidy.yml

@@ -63,6 +63,7 @@ jobs:
           cmake \
             -DVCPKG_TARGET_TRIPLET=x64-linux-release \
             -DVCPKG_HOST_TRIPLET=x64-linux-release \
+            -DCMAKE_POLICY_VERSION_MINIMUM=3.5 \
             -DCMAKE_C_COMPILER=clang-19 \
             -DCMAKE_CXX_COMPILER=clang++-19 \
             -DRESINSIGHT_USE_OPENMP=OFF \

.github/workflows/clazy-report.yml

@@ -70,6 +70,7 @@ jobs:
           cmake \
             -DVCPKG_TARGET_TRIPLET=x64-linux-release \
             -DVCPKG_HOST_TRIPLET=x64-linux-release \
+            -DCMAKE_POLICY_VERSION_MINIMUM=3.5 \
             -DCMAKE_C_COMPILER=clang-19 \
             -DCMAKE_CXX_COMPILER=clang++-19 \
             -DRESINSIGHT_USE_OPENMP=OFF \