…64847)

### What problem does this PR solve?

Problem Summary: `array_first` and `array_last` were rewritten through
`array_filter` before their lambda result type was checked against the
boolean filter argument. When the lambda returned a type that can be
implicitly cast to boolean, analysis reported an error instead of
applying the normal function coercion. This change gives `array_first`
and `array_last` their own signatures so the `array_map` result is
coerced to `array<boolean>` before the functions are rewritten to
`element_at(array_filter(...))`. It also keeps scalar function visitor
dispatch aligned with the new function shape.

### Release note

Fix `array_first` and `array_last` to allow lambda results that can be
implicitly cast to boolean.