Merge bitcoin/bitcoin#31679: cmake: Install internal binaries to <prefix>/libexec/

f49840dd90 doc: Fix typo in files.md (Ryan Ofsky)
f5cf0b1ccc bitcoin wrapper: improve help output (Ryan Ofsky)
c810b168b8 doc: Add description of installed files to files.md (Ryan Ofsky)
94ffd01a02 doc: Add release notes describing libexec/ binaries (Ryan Ofsky)
cd97905ebc cmake: Move internal binaries from bin/ to libexec/ (Ryan Ofsky)

Pull request description:

  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 of the PR is to introduce a distinction between internal and external binaries so starting with #31802, we can use IPC to implement features in new binaries without adding those binaries to the CLI. The change also helps reduce clutter in `bin/`, making it easier for users to identify useful tools to run. Summary of changes:

  - For **source builds** (i.e. developer builds) — There are no changes.
  - For **source installs** (i.e. `cmake --install` result) — `test_bitcoin`, `test_bitcoin-qt`, and `bench_bitcoin` are installed in `${CMAKE_PREFIX_PATH}/libexec` instead of `${CMAKE_PREFIX_PATH}/bin`, so they are no longer on the system `PATH`. However, they can still be invoked from the `libexec/` directory, or from the CLI as `bitcoin test`, `bitcoin test-gui`, and `bitcoin bench`, respectively.
  - For **binary releases** — Since `test_bitcoin` is the only test binary enabled in releases, the only change is moving `test_bitcoin` from `bin/` to `libexec/`.

  <details><summary>Details</summary>
  <p>

   The table below shows the install location of each binary after this change, and the availability of each binary.

  | Binary               | Location     | Availability         | Change                        |
  |----------------------|--------------|----------------------|-------------------------------|
  | `bitcoin`            | `bin/`       | 📦 Binary release (since #31375) | Unchanged                     |
  | `bitcoin-cli`        | `bin/`       | 📦 Binary release     | Unchanged                     |
  | `bitcoind`           | `bin/`       | 📦 Binary release     | Unchanged                     |
  | `bitcoin-qt`         | `bin/`       | 📦 Binary release     | Unchanged                     |
  | `bitcoin-tx`         | `bin/`       | 📦 Binary release     | Unchanged                     |
  | `bitcoin-util`       | `bin/`       | 📦 Binary release     | Unchanged                     |
  | `bitcoin-wallet`     | `bin/`       | 📦 Binary release     | Unchanged                     |
  | `bench_bitcoin`      | `libexec/`   | 🛠 Source build only  | Moved from `bin/`             |
  | `bitcoin-chainstate` | `libexec/`   | 🛠 Source build only  | Newly installed (was built)   |
  | `bitcoin-gui`        | `libexec/`   | 🛠 Source build only (until #31802) | Moved from `bin/`             |
  | `bitcoin-node`       | `libexec/`   | 🛠 Source build only (until #31802) | Moved from `bin/`             |
  | `test_bitcoin`       | `libexec/`    | 📦 Binary release     | Moved from `bin/`             |
  | `test_bitcoin-qt`    | `libexec/`   | 🛠 Source build only  | Moved from `bin/`             |

  </p>
  </details>

  ---

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/issues/28722).

ACKs for top commit:
  l0rinc:
    re-ACK f49840dd90
  Sjors:
    re-ACK f49840dd90
  achow101:
    ACK f49840dd90
  janb84:
    re ACK f49840dd90
  BrandonOdiwuor:
    Tested ACK f49840dd90
  hodlinator:
    re-ACK f49840dd90
  willcl-ark:
    utACK f49840dd90

Tree-SHA512: 858a2e1a53db11ee3c5c759bfdeea566f242b9ce5e8a898fa435222e41662b8184577c0dc2c4c058294b4de41d8cb3ba3e5d24c748c280efa4a3f84e3ec4344d

cmake/module/InstallBinaryComponent.cmake

@@ -7,14 +7,19 @@ include(GNUInstallDirs)
 
 function(install_binary_component component)
   cmake_parse_arguments(PARSE_ARGV 1
-    IC                # prefix
-    "HAS_MANPAGE"     # options
-    ""                # one_value_keywords
-    ""                # multi_value_keywords
+    IC                          # prefix
+    "HAS_MANPAGE;INTERNAL"      # options
+    ""                          # one_value_keywords
+    ""                          # multi_value_keywords
   )
   set(target_name ${component})
+  if(IC_INTERNAL)
+    set(runtime_dest ${CMAKE_INSTALL_LIBEXECDIR})
+  else()
+    set(runtime_dest ${CMAKE_INSTALL_BINDIR})
+  endif()
   install(TARGETS ${target_name}
-    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+    RUNTIME DESTINATION ${runtime_dest}
     COMPONENT ${component}
   )
   if(INSTALL_MAN AND IC_HAS_MANPAGE)