CI pipeline structure

The CI pipeline is composed of the following workflows:

• .github/workflows/build.yml: For building the device's firmware.
• .github/workflows/target-test.yml: For running tests on real hardware.
• .github/workflows/build-and-target-test.yml: Workflow that glues together build.yml and target-test.yml.
• .github/workflows/sonarcloud.yml: For building and running tests in emulation, and for running the SonarCloud analysis.
• .github/workflows/compliance.yml: For static compliance checks.
• .github/workflows/doc-sync.yml: For publishing documentation to Nordic Semiconductor's external documentation platform.
• .github/workflows/create-doc-bundle.yml: Creates the documentation bundle that the template uploads to Nordic Semiconductor's official documentation site.

The following events trigger the CI pipeline:

• Pull request: Runs build.yml, sonarcloud.yml, and compliance.yml. The pipeline runs no target tests on a pull request, to avoid instabilities.
• Push to main: Runs build-and-target-test.yml, sonarcloud.yml, and doc-sync.yml. The pipeline runs only the fast target tests, which avoids excessively time-consuming tests.
• Nightly: Runs build-and-target-test.yml with the full set of target tests. This includes slow tests, such as the full modem FOTA test and the application and MCUboot bootloader FOTA tests.