Replace the term “run” by something else where it is misleading

[jeltsch]

The section Representing clashes and larger-than-page entries in the compact documentation part of Database.LSMTree.Internal.IndexCompact uses the word “run” for things other than what is usually called runs in the context of LSMTs. This can be misleading, especially to newcomers. I suggest to replace “run” by something else, like “series” or “sequence”.