LWT `IF` (column_condition) duplicates the expression prepare and evaluation code. Annoyingly,
LWT IF semantics are a little different than the rest of CQL: a NULL equals NULL, whereas usually
NULL = NULL evaluates to NULL.
This series converts `IF` prepare and evaluate to use the standard expression code. We employ
expression rewriting to adjust for the slightly different semantics.
In a few places, we adjust LWT semantics to harmonize them with the rest of CQL. These are pointed
out in their own separate patches so the changes don't get lost in the flood.
Closes#12356
* github.com:scylladb/scylladb:
cql3: lwt: move IF clause expression construction to grammar
cql3: column_condition: evaluate column_condition as a single expression
cql3: lwt: allow negative list indexes in IF clause
cql3: lwt: do not short-circuit col[NULL] in IF clause
cql3: column_condition: convert _column to an expression
cql3: expr: generalize evaluation of subscript expressions
cql3: expr: introduce adjust_for_collection_as_maps()
cql3: update_parameters: use evaluation_inputs compatible row prefetch
cql3: expr: protect extract_column_value() from partial clustering keys
cql3: expr: extract extract_column_value() from evaluation machinery
cql3: selection: introduce selection_from_partition_slice
cql3: expr: move check for ordering on duration types from restrictions to prepare
cql3: expr: remove restrictions oper_is_slice() in favor of expr::is_slice()
cql3: column_condition: optimize LIKE with constant pattern after preparing
cql3: expr: add optimizer for LIKE with constant pattern
test: lib: add helper to evaluate an expression with bind variables but no table
cql3: column_condition: make the left-hand-side part of column_condition::raw
cql3: lwt: relax constraints on map subscripts and LIKE patterns
cql3: expr: fix search_and_replace() for subscripts
cql3: expr: fix function evaluation with NULL inputs
cql3: expr: add LWT IF clause variants of binary operators
cql3: expr: change evaluate_binop_sides to return more NULL information
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