doc: updates related to history modes & storage

What

Close #7329 (closed).

Updates some outdated details related to History modes and their handling in the storage subsystem.

Why

Some recent changes in protocol constants, RPCs, and others, have not been reflected in corresponding changes to all the impacted pages.

How

Answer the points in #7329 (closed) one by one:

• #7329 (comment 1959458118) on "a sliding window of history"
• #7329 (comment 1959459627) outdated preserved_cycles protocol parameter
• #7329 (comment 1959461794) on "By default, 1 additional cycle is kept"
• #7329 (comment 1959483022) the description of the three history modes is not self-contained
• #7329 (comment 1959486132) What about the context below the threshold, is it stored or discarded?
• #7329 (comment 1959492162) not very easy to get information
• #7329 (comment 1959518385) on "data may be pruned are when a cycle is completed"
• #7329 (comment 1959521661) meaning of "archived with the cemented cycles"
• #7329 (comment 1959543075) on "query the balances or staking rights before the current checkpoint"
• #7329 (comment 1959546971) outdated RPC /chains/main/checkpoint

Manually testing the MR

Check all the changes and estimate if they are correct and if they improve understanding.

Checklist

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