Don't demote job failed messages to debug.

[hjoliver]

Currently, we demote task messages to DEBUG level if they are more or less redundant with logged state changes.

However, this isn't ideal for job failure messages because,

• if there are any retries lined up, the state change straight to waiting, with no indication of failure, looks wrong
• job failures should really always be logged as critical (even if the graph is designed to handle it)

Example:

[scheduling]
    [[graph]]
        R1 = "a"
[runtime]
    [[a]]
        script = false
        execution retry delays = PT5S

Current:

This branch:

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