Merge various enhancements that were being held on a branch until after the

Merge various enhancements that were being held on a branch until after the
3.46.0 release.  (1) Allow arbitrary expressions in the second argument to
the RAISE() function. (2) Performance optimization to the OP_OpenRead and
OP_OpenWrite bytecode operators. (3) Allow FTS5 tables to be dropped even if
the associated tokenizer is not available.  (4) Performance optimizations in
FTS5.  (5) Generate better bytecode to improve performance of ONEROW scans.

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