This reverts commit 3830dde78f9bde7ebe01fddca49d5806d4e52bea.

Summary:
It serves as a replacement for `kdbusaddons_generate_dbus_service_file`.

An application can be a DBus-activated service just fine without using KDBusAddons.
Moreover, this new module uses named arguments for future-proofing, and adds support for specifying a `SystemdService`.
It also cleans up the confusion on what the "path" is about: Rather than requiring to specify executable and path separately, we just extract the executable file name on Windows, if necessary.

Usage:
```
ecm_generate_dbus_service_file(NAME org.kde.kded5
                               EXECUTABLE ${KDE_INSTALL_FULL_BINDIR}/kded5
                               SYSTEMD_SERVICE plasma-kded)
```

Test Plan:
* Was able to generate a kded service file
* Was able to generate a kded service file with `SystemdUnit`
* Verified that it moaned when executable wasn't an absolute path
* Untested on Windwos

Reviewers: #frameworks, davidedmundson, kossebau, kfunk, habacker

Subscribers: kde-frameworks-devel, kde-buildsystem

Tags: #frameworks, #build_system

Differential Revision: https://phabricator.kde.org/D29051

Summary:
This, as the name suggests, configures a file and installs it.

It's not very complicated but it's a repeated pattern in plasma that
gets quite messy dealing with temporary files.

Test Plan: Used in a project

Reviewers: #build_system

Subscribers: apol, kossebau, pino, kde-frameworks-devel, kde-buildsystem

Tags: #frameworks, #build_system

Differential Revision: https://phabricator.kde.org/D28355

This is useful if a library intends to reparse the original wayland.xml
file instead of using the pregenerated headers.

Lexer for CMake could not parse this broken grammar,
because it is ".cmake.in", not just ".cmake".

CMake itself solves this problems by declaring such code blocks
as generic "::" blocks instead. For example, take a look at the
last code block at CMakePackageConfigHelpers help page:

 - https://cmake.org/cmake/help/v3.18/module/CMakePackageConfigHelpers.html#example-generating-package-files
 - https://github.com/Kitware/CMake/blob/0464298956a204578aa8421ca0b84c089a97e0aa/Modules/CMakePackageConfigHelpers.cmake#L208

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