[MPH-218] Embed original exceptions as cause in DescribeMojo

**[Elliotte Rusty Harold](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=elharo)** opened **[MPH-218](https://issues.apache.org/jira/browse/MPH-218?redirect=false)** and commented

{{ return output;
} catch (SecurityException e) {
throw new MojoFailureException("SecurityException: " + e.getMessage());
} catch (IllegalArgumentException e) {
throw new MojoFailureException("IllegalArgumentException: " + e.getMessage());
} catch (NoSuchMethodException e) {
throw new MojoFailureException("NoSuchMethodException: " + e.getMessage());
} catch (IllegalAccessException e) {
throw new MojoFailureException("IllegalAccessException: " + e.getMessage());
} catch (InvocationTargetException e) {
Throwable cause = e.getCause();

if (cause instanceof NegativeArraySizeException) {
throw new MojoFailureException("NegativeArraySizeException: " + cause.getMessage());
}

throw new MojoFailureException("InvocationTargetException: " + e.getMessage());
}}}

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No further details from [MPH-218](https://issues.apache.org/jira/browse/MPH-218?redirect=false)

Start at the exception-handling code in DescribeMojo shown in the issue and inspect how each caught exception is wrapped. Confirm that the resulting MojoFailureException retains the original exception as its cause, including InvocationTargetException paths; use the relevant project tests or add coverage if available.

Written by the indexing model from the issue text.