Back out changes [00286ca5d998d802] and [6844ede29e1dac93] (replacing the

Back out changes [00286ca5d998d802] and [6844ede29e1dac93] (replacing the
associated branches with NEVER()) and add a single new test to
btreeOverwriteCell() that detects when an overflow pages is also mapped
into a b-tree page and raises and immediate SQLITE_CORRUPT error before
making any changes.
dbsqlfuzz 81791bd980fe6935ff2c7334ec8bef11c1c12b82 and others.

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