1953 defensive testing extrinsic (#1998)

# Description

The `trigger_defensive` call has been added to the `root-testing`
pallet. The idea is to have this pallet running on `Rococo/Westend` and
use it to verify if the runtime monitoring works end-to-end.

To accomplish this, `trigger_defensive` dispatches an event when it is
called.

Closes #1953

# Checklist

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- [ ] I have made corresponding changes to the documentation (if
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- [ ] I have added tests that prove my fix is effective or that my
feature works (if applicable)

You can remove the "Checklist" section once all have been checked. Thank
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Signed-off-by: Oliver Tale-Yazdi <[email protected]>
Co-authored-by: Oliver Tale-Yazdi <[email protected]>