This commit introduces slight behaviour change. Previously, the
GUI status bar would be updated for most warnings, namely
UNKNOWN_NEW_RULES_ACTIVATED, CLOCK_OUT_OF_SYNC and
PRE_RELEASE_TEST_BUILD, but not for LARGE_WORK_INVALID_CHAIN
(and not for FATAL_INTERNAL_ERROR, but that is not really
meaningful).
Fix this by always updating the status bar when the warnings are
changed.
Instead of having separate warning functions (and globals) for each
different warning that can be raised, encapsulate this logic into
a single class and allow to (un)set any number of warnings.
Introduces behaviour change:
- the `-alertnotify` command is executed for all
`KernelNotifications::warningSet` calls, which now also covers the
`LARGE_WORK_INVALID_CHAIN` warning.
- previously, warnings were returned based on a predetermined order,
e.g. with the "pre-release test build" warning always first. This
is no longer the case, and Warnings::GetMessages() will return
messages sorted by the id of the warning.
Removes warnings.cpp from kernel.
This helper class is an alternative to CMedianFilter, but without a
lot of the special logic and exceptions that we needed while it was
still used for consensus.
