[Build] Removed gRPC_PROTOBUF_PACKAGE_TYPE, supporting config only (#32988)

`FindProtobuf` isn't working as Protobuf began to use Abseil so gRPC is
now using `CONFIG` mode for protobuf module
(Context: https://gitlab.kitware.com/cmake/cmake/-/issues/24321)

CMakeLists.txt

@@ -85,9 +85,6 @@ set_property(CACHE gRPC_SSL_PROVIDER PROPERTY STRINGS "module" "package")
 set(gRPC_PROTOBUF_PROVIDER "module" CACHE STRING "Provider of protobuf library")
 set_property(CACHE gRPC_PROTOBUF_PROVIDER PROPERTY STRINGS "module" "package")
 
-set(gRPC_PROTOBUF_PACKAGE_TYPE "" CACHE STRING "Algorithm for searching protobuf package")
-set_property(CACHE gRPC_PROTOBUF_PACKAGE_TYPE PROPERTY STRINGS "CONFIG" "MODULE")
-
 if(gRPC_BUILD_TESTS)
   set(gRPC_BENCHMARK_PROVIDER "module" CACHE STRING "Provider of benchmark library")
   set_property(CACHE gRPC_BENCHMARK_PROVIDER PROPERTY STRINGS "module" "package")

cmake/protobuf.cmake

@@ -55,12 +55,8 @@ if(gRPC_PROTOBUF_PROVIDER STREQUAL "module")
     set(gRPC_INSTALL FALSE)
   endif()
 elseif(gRPC_PROTOBUF_PROVIDER STREQUAL "package")
-  find_package(Protobuf REQUIRED ${gRPC_PROTOBUF_PACKAGE_TYPE})
+  find_package(Protobuf REQUIRED CONFIG)
 
-  # {Protobuf,PROTOBUF}_FOUND is defined based on find_package type ("MODULE" vs "CONFIG").
-  # For "MODULE", the case has also changed between cmake 3.5 and 3.6.
-  # We use the legacy uppercase version for *_LIBRARIES AND *_INCLUDE_DIRS variables
-  # as newer cmake versions provide them too for backward compatibility.
   if(Protobuf_FOUND OR PROTOBUF_FOUND)
     if(TARGET protobuf::${_gRPC_PROTOBUF_LIBRARY_NAME})
       set(_gRPC_PROTOBUF_LIBRARIES protobuf::${_gRPC_PROTOBUF_LIBRARY_NAME})
@@ -90,6 +86,6 @@ elseif(gRPC_PROTOBUF_PROVIDER STREQUAL "package")
         set(_gRPC_PROTOBUF_PROTOC_EXECUTABLE ${PROTOBUF_PROTOC_EXECUTABLE})
       endif()
     endif()
-    set(_gRPC_FIND_PROTOBUF "if(NOT Protobuf_FOUND AND NOT PROTOBUF_FOUND)\n  find_package(Protobuf ${gRPC_PROTOBUF_PACKAGE_TYPE})\nendif()")
+    set(_gRPC_FIND_PROTOBUF "find_dependency(Protobuf CONFIG)")
   endif()
 endif()

examples/cpp/helloworld/cmake_externalproject/CMakeLists.txt

@@ -119,7 +119,6 @@ ExternalProject_Add(grpc
         -DgRPC_BUILD_MSVC_MP_COUNT:STRING=-1
         -Dutf8_range_DIR:STRING=${CMAKE_CURRENT_BINARY_DIR}/utf8_range/lib/cmake/utf8_range
         -DgRPC_PROTOBUF_PROVIDER:STRING=package
-        -DgRPC_PROTOBUF_PACKAGE_TYPE:STRING=CONFIG
         -DProtobuf_DIR:PATH=${_FINDPACKAGE_PROTOBUF_CONFIG_DIR}
         -DgRPC_RE2_PROVIDER:STRING=package
         -Dre2_DIR:STRING=${CMAKE_CURRENT_BINARY_DIR}/re2/lib/cmake/re2

templates/CMakeLists.txt.template

@@ -217,9 +217,6 @@
   set(gRPC_PROTOBUF_PROVIDER "module" CACHE STRING "Provider of protobuf library")
   set_property(CACHE gRPC_PROTOBUF_PROVIDER PROPERTY STRINGS "module" "package")
 
-  set(gRPC_PROTOBUF_PACKAGE_TYPE "" CACHE STRING "Algorithm for searching protobuf package")
-  set_property(CACHE gRPC_PROTOBUF_PACKAGE_TYPE PROPERTY STRINGS "CONFIG" "MODULE")
-
   if(gRPC_BUILD_TESTS)
     set(gRPC_BENCHMARK_PROVIDER "module" CACHE STRING "Provider of benchmark library")
     set_property(CACHE gRPC_BENCHMARK_PROVIDER PROPERTY STRINGS "module" "package")

test/distrib/cpp/run_distrib_test_cmake.bat

@@ -99,7 +99,6 @@ cmake ^
   -DgRPC_BUILD_MSVC_MP_COUNT=-1 ^
   -DgRPC_ABSL_PROVIDER=package ^
   -DgRPC_CARES_PROVIDER=package ^
-  -DgRPC_PROTOBUF_PACKAGE_TYPE=CONFIG ^
   -DgRPC_PROTOBUF_PROVIDER=package ^
   -DProtobuf_USE_STATIC_LIBS=ON ^
   -DgRPC_RE2_PROVIDER=package ^

test/distrib/cpp/run_distrib_test_cmake.sh

@@ -75,7 +75,6 @@ cmake \
   -DgRPC_BUILD_TESTS=OFF \
   -DgRPC_CARES_PROVIDER=package \
   -DgRPC_ABSL_PROVIDER=package \
-  -DgRPC_PROTOBUF_PACKAGE_TYPE=CONFIG \
   -DgRPC_PROTOBUF_PROVIDER=package \
   -DgRPC_RE2_PROVIDER=package \
   -DgRPC_SSL_PROVIDER=package \

test/distrib/cpp/run_distrib_test_cmake_pkgconfig.sh

@@ -81,7 +81,6 @@ cmake \
   -DgRPC_BUILD_TESTS=OFF \
   -DgRPC_ABSL_PROVIDER=package \
   -DgRPC_CARES_PROVIDER=package \
-  -DgRPC_PROTOBUF_PACKAGE_TYPE=CONFIG \
   -DgRPC_PROTOBUF_PROVIDER=package \
   -Dutf8_range_DIR=/usr/local/lib/cmake/utf8_range \
   -DgRPC_RE2_PROVIDER=package \