We can avoid some test set up code repetitions and make it
cleaner.

It's clearer and also reduces their scope.

Just for cleaning up some repetition in tests.

Set default expectation on PerformHttpRequest for
the authentication and token fetch.

They were not needed.

…sage

Replaced raw time_t/int with std::chrono::milliseconds for clarity and type safety.
This removes ambiguity in time units, prevents conversion errors, and improves readability.
No overhead, as std::chrono::milliseconds is just a strongly-typed integer.

We keep this commit instead of rebasing, so
we can easily bring it back once we are ready
to enable this feature as well.

First, the matching header file for the source file.
Second, includes from the agent.
Third, third party libraries.
Last, standard c++ includes.

This commit also brings timehelper, which is needed to
add a timestamp to the shutdown event messages.