First refactor of compaction docs

[techdocsmith]

#10897

First pass refactor / update of compaction docs

Updates to "Data management" topic as follows:

• Adds an introduction that describes the content in the topic.
• Removes a duplicated section about "Schema changes" and leaves it in design/segments.md

Adds a new topic "Compaction" that defines compaction and automatic compaction as a strategy for segment optimization.

• Use cases for compaction. Data handling with compaction. Describes compaction task configuration."
• This includes the behavior for Keep query granularity of compacted segments after compaction #10856
• This includes the behavior for Add query granularity to compaction task #10900

Repairs links for the refactor above.

This PR doesn't handle the remaining task of identifying reindexing and compaction as data management tasks for existing data and comparing the use cases between the two. This should come in a subsequent PR.

cc: @maytasm, @suneet-s , @loquisgon , @sthetland

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This PR has:

• been self-reviewed.
• added documentation for new or modified features or behaviors.

[2bethere]

Thanks for putting this up! I think it's a much-needed improvement. Added some comments.

[sthetland]

Comments & suggestions below.. Looks good though! It makes compaction clearer.

[suneet-s]

I echo others comments on this PR. This is a huge improvement - thank you @techdocsmith ! I haven't verified the correctness of how exactly compaction works, or the details of the different tuning knobs

Some overall structural feedback (doesn't need to be addressed in this PR):

• I think the data management doc should be broken into a few separate docs. Seeing compaction pulled out of there - it feels like data management would be a good landing page - that then points you to "getting data in", "Optimizing data", "Updating data"(maybe) and "Deleting data" This is obviously beyond the scope of this PR, but I think it's worth mentioning because it adds structure around how to think about data and managing data in Druid.
• Data management also talks about lookups, while the rest of the doc talks about datasources. This seemed a little out of place when I was reading locally. I don't have a suggestion for how to structure this right now, but wanted to surface it in case you had better ideas.
• The compaction page currently talks about the what. I wonder if it needs to be split into 2 pages (or sections), one that spells out the "why should I care/ I want to do..." a little bit more, and another that spells out "how do I do that". Maybe it can be intertwined in the same page?
• I really like the distinction between auto-compaction and manual compaction. However the page doesn't link to anything that tells me how to use auto-compaction, but it does link to something about manual compaction. Are there instructions for auto-compaction elsewhere?
• There are some known differences between auto-compaction and manual compaction. Support for queryGranularity is one right now. Do you think we should call this out in the section that talks about the differences between the 2. This is tricky, because it's like a gap in functionality - but it's a gotcha I think users will want to know about.

[suneet-s]

Docs failure looks legit

Could not find self anchor '#compaction-tuningconfig' in './build/ApacheDruid/docs/configuration/index.html'
Could not find './native_batch.md' linked from './build/ApacheDruid/docs/ingestion/compaction.html'
Could not find '../native-batch.md' linked from './build/ApacheDruid/docs/ingestion/compaction.html'
Could not find '../data-management.md' linked from './build/ApacheDruid/docs/ingestion/index.html'
Could not find '../compaction.md' linked from './build/ApacheDruid/docs/ingestion/index.html'
There are 5 issues

[techdocsmith]

Apologize for that @suneet-s , I fixed links and spelling in a later commit.