v0.0.81: [Wasm] Provide join cost models closer to reality.

Provide cost models for the WebAssembly join implementations that are
closer to reality and replace the former hard-coded values.  This is
still a very naïve and abstract model.  We could and should improve
these models in the future based on empirical data.

v0.0.80: [Wasm] Adapt the cost function of `Filter`.

`Filter` must be more expensive than `LazyDisjunctiveFilter` on
disjunctive predicates.

v0.0.79: [Wasm] Implement `LazyDisjunctiveFilter`.

Provide physical implementation `LazyDisjunctiveFilter` for algebraic
`DisjunctiveFilterOperator` and its corresponding `Match` class.

v0.0.78

[PE] Add searches with cost-based pruning to HSPE.

v0.0.77

[Benchmark] Update chart_config of experiments in .pgsql file

v0.0.76: [Util] Add `is_allocator` concept

Without this concept, compiler would pick the templated
perfect-forwarding constructor of `doubly_linked_list`
over its copy constructor for `non const` arguments.

v0.0.75: [Backend] Update backends for minimized `Schema`.

The prior commit introduced a more rigorous minimization of `Schema`s of
`Operator`s in a plan.  This commit makes the necessary changes in the
backends to handle the new `Schema`.

So far, the `Interpreter` relied on the `Schema` not being exactly
*minimal* but simply a concatenation of the `Schema`s of both sides of a
join.  This commit fixes the implementation of the simple-hash join to
correctly use the minimized schema.  Further, we drop the requirement
that `Tuple`s be simply concatenated.

v0.0.74

[AST] Make `Expr` target references red in ASTDot.

v0.0.73: [Wasm] Improve `Decimal` class.

- Remove superfluous methods.  The once inherited from `Expr<T>` are
  already what we need.
- *Delete* (with `require false`) certain operators and methods that are
  not supported by `Decimal`, e.g. `rotl` or `neg`.

v0.0.72

[Benchmark] Fix mutable config name of experiment tpc-h/q12