effects: redesign the `Effects` data structure (#46180)
This commit stops representing each effect property as `TriState` but
represents them as `UInt8` or `Bool` directly. The motivation is that
the tri-state representation hasn't been used actually and rather the
incoming improvements on the analysis want to represent some effects
as bits to propagate more information. For example, `:consistent`-cy
is represented as `UInt8`, where currently it has the following meanings:
- `const ALWAYS_TRUE = 0x00`
- `const ALWAYS_FALSE = 0x01`
- `const CONSISTENT_IF_NOTRETURNED = 0x02`: the `:consistent`-cy can be
refined using the return type information later in a case when
allocated mutable objects are never returned
and I'm also planning to add `const CONSISTENT_IF_NOGLOBAL = 0x04`, that
allows us to improve the analysis accuracy by refining the `:consistent`-cy
using new effect property that tracks escapability of mutable objects
(and actually the similar improvement can be added for `:effect_free`-ness
by changing its type from `Bool` to `UInt8` as like `:consistent`-cy).
