[ML] File Data Viz should allow retry with overrides when initial analysis fails #38868
Description
(Split out from part 4 of #36880.)
After uploading a file to the file data visualizer, if the timestamp format is not recognised at all then this can lead to the whole structure analysis returning an error. At the moment it is only possible to override the timestamp if the initial attempt at analysis succeeded. It would be nice if the user was able to enter overrides after an error on the initial analysis, to enable them to import a file in situations when giving hints to the structure analysis would allow it to succeed.
Although the timestamp is the most likely thing to need overriding, other decisions could be usefully overridden too in the event of an initial analysis failure. One example is the high level format, and, for delimited formats, the delimiter. If elastic/elasticsearch#38890 is implemented then this would allow not-quite-CSV files to be imported. And if elastic/elasticsearch#55219 is implemented then this would allow semi-structured log files with no timestamp to be imported.