refactor(nm): NMDBusConnector class refactor

[pierantoniomerlino]

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This PR perform a refactor of the NMDbusConnector class. In particular, it adds the apply(String deviceId) method that is used by the NMConfigurationEnforcementHandler to apply the configuration to a single device/interface and it rewrites the doApply method in a simpler way.

[mattdibi]

For documentation purpose I will report here my findings on a new behaviour with this PR.

I performed a couple of tests using a Telit HE910 modem. When connected this device creates an additional NetworkManager device of type PPP.

When a new configuration is issued (for example disconnecting the modem) the following stacktrace appears in the log:

This is due to the fact that the PPP device (which is created upon the modem connecting), disappears and its dbus path invalidated. Since we're iterating over devices here:

https://github.com/eclipse/kura/blob/2cdcc7677f408857165ff164a60c784805639d91/kura/org.eclipse.kura.nm/src/main/java/org/eclipse/kura/nm/NMDbusConnector.java#L316-L324

when we get to the PPP device, it doesn't exist anymore and the DBus path is invalidated. This is all correctly handled by the code (the exception is handled and all remaining operation work as expected). No code chages are required here IMO.

[mattdibi]

LGTM

[github-actions]

The backport to release-5.3.0 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-release-5.3.0 release-5.3.0
# Navigate to the new working tree
cd .worktrees/backport-release-5.3.0
# Create a new branch
git switch --create backport-4517-to-release-5.3.0
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 841a7693f9df37d804cbd9179f1b756471a1f2f0
# Push it to GitHub
git push --set-upstream origin backport-4517-to-release-5.3.0
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-release-5.3.0

Then, create a pull request where the base branch is release-5.3.0 and the compare/head branch is backport-4517-to-release-5.3.0.