Add deprecation warnings for policies CMP0108 and below

The OLD behaviors of all policies are deprecated, but only by
documentation.  Add an explicit deprecation diagnostic for policies
introduced in CMake 3.18 and below to encourage projects to port
away from setting policies to OLD.

Source/cmMakefile.cxx

@@ -4470,12 +4470,12 @@ bool cmMakefile::SetPolicy(cmPolicies::PolicyID id,
   }
 
   // Deprecate old policies.
-  if (status == cmPolicies::OLD && id <= cmPolicies::CMP0102 &&
+  if (status == cmPolicies::OLD && id <= cmPolicies::CMP0108 &&
       !(this->GetCMakeInstance()->GetIsInTryCompile() &&
         (
           // Policies set by cmCoreTryCompile::TryCompileCode.
           id == cmPolicies::CMP0065 || id == cmPolicies::CMP0083 ||
-          id == cmPolicies::CMP0091)) &&
+          id == cmPolicies::CMP0091 || id == cmPolicies::CMP0104)) &&
       (!this->IsSet("CMAKE_WARN_DEPRECATED") ||
        this->IsOn("CMAKE_WARN_DEPRECATED"))) {
     this->IssueMessage(MessageType::DEPRECATION_WARNING,

Tests/RunCMake/CMP0104/CMP0104-OLD-stderr.txt

@@ -0,0 +1,10 @@
+^CMake Deprecation Warning at CMP0104-OLD.cmake:[0-9]+ \(cmake_policy\):
+  The OLD behavior for policy CMP0104 will be removed from a future version
+  of CMake.
+
+  The cmake-policies\(7\) manual explains that the OLD behaviors of all
+  policies are deprecated and that a policy should be set to OLD only under
+  specific short-term circumstances.  Projects should be ported to the NEW
+  behavior and not rely on setting a policy to OLD.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/CMP0106/CMP0106-OLD-stderr.txt

@@ -0,0 +1,10 @@
+^CMake Deprecation Warning at CMP0106-OLD.cmake:[0-9]+ \(cmake_policy\):
+  The OLD behavior for policy CMP0106 will be removed from a future version
+  of CMake.
+
+  The cmake-policies\(7\) manual explains that the OLD behaviors of all
+  policies are deprecated and that a policy should be set to OLD only under
+  specific short-term circumstances.  Projects should be ported to the NEW
+  behavior and not rely on setting a policy to OLD.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/alias_targets/duplicate-target-CMP0107-OLD-stderr.txt

@@ -0,0 +1,10 @@
+^CMake Deprecation Warning at duplicate-target-CMP0107-OLD.cmake:[0-9]+ \(cmake_policy\):
+  The OLD behavior for policy CMP0107 will be removed from a future version
+  of CMake.
+
+  The cmake-policies\(7\) manual explains that the OLD behaviors of all
+  policies are deprecated and that a policy should be set to OLD only under
+  specific short-term circumstances.  Projects should be ported to the NEW
+  behavior and not rely on setting a policy to OLD.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/export/Repeat-CMP0103-OLD-stderr.txt

@@ -0,0 +1,10 @@
+^CMake Deprecation Warning at Repeat-CMP0103-OLD.cmake:[0-9]+ \(cmake_policy\):
+  The OLD behavior for policy CMP0103 will be removed from a future version
+  of CMake.
+
+  The cmake-policies\(7\) manual explains that the OLD behaviors of all
+  policies are deprecated and that a policy should be set to OLD only under
+  specific short-term circumstances.  Projects should be ported to the NEW
+  behavior and not rely on setting a policy to OLD.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)$

Tests/RunCMake/target_link_libraries/CMP0108-OLD-self-link-stderr.txt

@@ -0,0 +1,10 @@
+^CMake Deprecation Warning at CMP0108-OLD-self-link.cmake:[0-9]+ \(cmake_policy\):
+  The OLD behavior for policy CMP0108 will be removed from a future version
+  of CMake.
+
+  The cmake-policies\(7\) manual explains that the OLD behaviors of all
+  policies are deprecated and that a policy should be set to OLD only under
+  specific short-term circumstances.  Projects should be ported to the NEW
+  behavior and not rely on setting a policy to OLD.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)$