Merge bitcoin/bitcoin#31181: cmake: Revamp FindLibevent module

5a96767e3f depends, libevent: Do not install *.pc files and remove patches for them (Hennadii Stepanov)
ffda355b5a cmake, refactor: Move `HAVE_EVHTTP_...` to `libevent` interface (Hennadii Stepanov)
b619bdc330 cmake: Revamp `FindLibevent` module (Hennadii Stepanov)

Pull request description:

  This PR generalizes the use of `find_package` / `pkg_check_modules`, prioritizing the former.

  Addresses https://github.com/bitcoin/bitcoin/pull/30903#issuecomment-2444700876:
  > We should also follow up with refactoring the libevent module, to more generically use CMake/pkg-config, rather than restricting the CMake usage to `vcpkg`. At that point, we'd likely be able to dump pkg-config for the depends path entirely.

  Similar to https://github.com/bitcoin/bitcoin/pull/30903.

ACKs for top commit:
  fanquake:
    ACK 5a96767e3f

Tree-SHA512: 181020c16ccd2821e718c73f264badcdc5e62980c4a8d9691e759efe2ea00da2326e26308d1dcfdeac01e9e27930428ecace9f36941deee951b751b138d7266c

src/test/CMakeLists.txt

@@ -154,7 +154,7 @@ target_link_libraries(test_bitcoin
   minisketch
   secp256k1
   Boost::headers
-  $<TARGET_NAME_IF_EXISTS:libevent::libevent>
+  libevent::extra
 )
 
 if(ENABLE_WALLET)

src/test/fuzz/CMakeLists.txt

@@ -140,7 +140,7 @@ target_link_libraries(fuzz
   univalue
   secp256k1
   Boost::headers
-  $<TARGET_NAME_IF_EXISTS:libevent::libevent>
+  libevent::extra
 )
 
 if(ENABLE_WALLET)