Upgrade mixed syntax

[oliver-sanders]

Closes #2094

Note: #2094 was reported with 6.11.2, I can backport this if we are planning another 6.11.x release.

1) Fixes a problem in the upgrader class whereby the following config:

[runtime]
    [[foo]]
        [[[job submission]]]
            zarquon = True

Would fail to be caught by this upgrader:

u = upgrader(cfg, descr)
u.obsolete(
    '7.0.0',
    ['runtime', '__MANY__', 'job', 'zarquon'])
u.upgrade()

Old behaviour:

$ cylc validate .
Illegal item: [runtime][foo][job]zarquon

New behaviour:

[osanders@eld668 temp2]$ cylc validate --verbose .
...
WARNING: deprecated items were automatically upgraded in 'suite definition':
 * (7.0.0) [runtime][foo][job][zarquon] - DELETED (OBSOLETE)
...
Valid for cylc-7.0.0-dirty

2. Fixes upgrading of mixed-syntax job submission/job sections

The following config ...

...
[runtime]
    [[foo]]
        command scripting = sleep 5  # old
        [[[job submission]]]         # old
            batch system = at        # new
            retry delays = PT1M      # old
        [[[event hooks]]]            # old
            failed handler = true    # old/new

Will now parse correctly:

$ cylc get-config --sparse . -i [runtime]
[[root]]
[[foo]]
    script = sleep 5
    [[[events]]]
        failed handler = true
    [[[job]]]
        batch system = at
        submission retry delays = PT1M

With the following notices from validate:

[osanders@eld668 temp2]$ cylc validate --verbose --verbose .
...
WARNING: deprecated items were automatically upgraded in 'suite definition':
 * (6.4.0) [runtime][foo][command scripting] -> [runtime][foo][script] - value unchanged
 * (6.11.0) [runtime][foo][event hooks] -> [runtime][foo][events] - value unchanged
 * (6.11.0) [runtime][foo][job submission] -> [runtime][foo][job] - value unchanged
 * (6.11.0) [runtime][foo][job][retry delays] -> [runtime][foo][job][submission retry delays] - value
...
Valid for cylc-7.0.0-dirty

Caveat: the deprecation warning now reads [runtime][foo][job][retry delays] rather than [runtime][foo][job submission][retry delays] which could be a little cryptic.

3) Upgrade section headings rather than the settings within them (in cylc/cfgspec/suite.py)

e.g. upgrade [event handlers] to [events] rather than upgrading [event handlers]failed handler to [events]failed handler then [event handlers]xyz to [events]xyz ...

@arjclark @matthewrmshin @hjoliver Whoever's around please debate / review.

[matthewrmshin]

Looks good.

[hjoliver]

@oliver-sanders - we are planning another 6.11.x release now; could you backport this plz.

[hjoliver]

Good.

[hjoliver]

@oliver-sanders - this deprecate call is now redundant - the 'old' and 'new' args are the same (sorry, I missed this yesterday!)

[oliver-sanders]

Well spotted! I've updated the back-port and have put up a new pull (#2103) for 7.0.x.