cmake: Move internal binaries from bin/ to libexec/

This change moves binaries that are not typically invoked directly by users
from the `bin/` directory to the `libexec/` directory in CMake installs and
binary releases. The goal is to simplify the contents of `bin/` for end users
while still making all binaries available when needed. After this change, the
binaries remaining in `bin/` are:

- bitcoin
- bitcoin-cli
- bitcoind
- bitcoin-qt
- bitcoin-tx
- bitcoin-util
- bitcoin-wallet

And the binaries that are moved to `libexec/` are:

- bench_bitcoin
- bitcoin-chainstate(*)
- bitcoin-gui(***)
- bitcoin-node(***)
- test_bitcoin(**)
- test_bitcoin-qt

(*) bitcoin-chainstate was previously missing an install rule and was actually
not installed even when it was enabled.

(**) test_bitcoin is the only libexec/ binary that is currently included in
bitcoin binary releases. The others are only installed when building from
source with relevant cmake options enabled.

(***) bitcoin-node and bitcoin-gui are not currently built by default or
included in binary releases but both of these changes are planned and
implemented in #31802

src/qt/CMakeLists.txt

@@ -282,7 +282,7 @@ if(ENABLE_IPC)
     bitcoin_ipc
   )
   import_plugins(bitcoin-gui)
-  install_binary_component(bitcoin-gui)
+  install_binary_component(bitcoin-gui INTERNAL)
   if(WIN32)
     set_target_properties(bitcoin-gui PROPERTIES WIN32_EXECUTABLE TRUE)
   endif()

src/qt/test/CMakeLists.txt

@@ -45,4 +45,4 @@ if(WIN32 AND VCPKG_TARGET_TRIPLET)
   )
 endif()
 
-install_binary_component(test_bitcoin-qt)
+install_binary_component(test_bitcoin-qt INTERNAL)