♻️🎨 Code cleanup and refactors (#798)

## Description

Starting the year with some obligatory code cleanup and refactors.
The individual commits and the commit messages should more or less
convey the bigger changes.
For the most part, it's really all about defining clearer interfaces and
following some new clang-tidy suggestions.

## Checklist:

<!---
This checklist serves as a reminder of a couple of things that ensure
your pull request will be merged swiftly.
-->

- [x] The pull request only contains commits that are related to it.
- [x] I have added appropriate tests and documentation.
- [ ] I have made sure that all CI jobs on GitHub pass.
- [ ] The pull request introduces no new warnings and follows the
project's style guidelines.

cmake/StandardProjectSettings.cmake

@@ -28,20 +28,6 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS
     ON
     CACHE BOOL "Export compile commands" FORCE)
 
-option(ENABLE_IPO "Enable Interprocedural Optimization, aka Link Time Optimization (LTO)" OFF)
-if(ENABLE_IPO)
-  include(CheckIPOSupported)
-  check_ipo_supported(RESULT ipo_supported OUTPUT ipo_output)
-  # enable inter-procedural optimization if it is supported
-  if(ipo_supported)
-    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION
-        TRUE
-        CACHE BOOL "Enable Interprocedural Optimization" FORCE)
-  else()
-    message(DEBUG "IPO is not supported: ${ipo_output}")
-  endif()
-endif()
-
 if(CMAKE_CXX_COMPILER_ID MATCHES ".*Clang")
   add_compile_options(-fcolor-diagnostics)
 elseif(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
@@ -70,3 +56,21 @@ if(DEPLOY)
       "10.15"
       CACHE STRING "" FORCE)
 endif()
+
+if(NOT DEPLOY)
+  option(ENABLE_IPO "Enable Interprocedural Optimization, aka Link Time Optimization (LTO)" ON)
+else()
+  option(ENABLE_IPO "Enable Interprocedural Optimization, aka Link Time Optimization (LTO)" OFF)
+endif()
+if(ENABLE_IPO)
+  include(CheckIPOSupported)
+  check_ipo_supported(RESULT ipo_supported OUTPUT ipo_output)
+  # enable inter-procedural optimization if it is supported
+  if(ipo_supported)
+    set(CMAKE_INTERPROCEDURAL_OPTIMIZATION
+        TRUE
+        CACHE BOOL "Enable Interprocedural Optimization" FORCE)
+  else()
+    message(DEBUG "IPO is not supported: ${ipo_output}")
+  endif()
+endif()