feat(observability): Update log levels for transforms

[spencergilbert]

Signed-off-by: Spencer Gilbert spencer.gilbert@gmail.com

I've updated the log levels of several transforms to better match why it's being logged.

• add_tags: both of these logs are emitted when Vector takes the action as configured (only emits overwritten message when overwrite = true)
• grok_parser: set missing field log to warn based on a quick chat with @binarylogic, conversion failure seems like a warning or maybe even an error?
• regex_parser: matched behaviour with grok_parser
• remove_fields: also discussed with @binarylogic - if you're trying to remove a field and it already isn't there, that seems ok
• rename_events: overwritten is again the configured behaviour like add_tags, warn on missing field as above
• split: warn on missing again, and another log for converting which I set to warn but could be error?
• tag_cardinality_limit: these all appear to be logging when the transform is carrying out its task, maybe it could be info though?
• tokenizer: warn on missing again, and another log for converting which I set to warn but could be error?

[binarylogic]

Thanks!