fix(NewRelicContextFormatter): add cause and context to stack traces

[sweco]

Overview

NewRelicContextFormatter logs stack traces without causes which makes many errors hard to debug.

Let's take a look at the following code:

try:
    try:
        raise ValueError("First exception")
    except:
        raise ValueError("Second exception")
except Exception as e:
    logging.error("Encountered error", exc_info=e)

Before the PR, the exception message looked as follows:

  File ".../newrelic_exception_cause.py", line 60, in <module>
    raise ValueError("Second exception")

After the PR, it shows more details on the first cause:

Traceback (most recent call last):
  File ".../newrelic_exception_cause.py", line 58, in <module>
    raise ValueError("First exception")
ValueError: First exception
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File ".../newrelic_exception_cause.py", line 60, in <module>
    raise ValueError("Second exception")
ValueError: Second exception

Related Github Issue

No Github issue created.

Testing

Tests were updated to test a particular case where exception has a cause.

[CLAassistant]

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