support Arrow on 1.9+ via pkg extension

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (0480e3f) 89.67% compared to head (9155058) 89.68%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #274 +/- ## ========================================== + Coverage 89.67% 89.68% +0.01% ========================================== Files 10 11 +1 Lines 1821 1823 +2 ========================================== + Hits 1633 1635 +2 Misses 188 188 ```

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[palday]

@quinnj 1.9 isn't the new LTS yet -- LTS can't be declared until the following release is out. But that said, I think bumping compat to 1.9 for a new feature in an otherwise stable package is a good choice and that's what I've done here. We can revisit this decision is there is a loud outcry from 1.6 users. 😄

[iamed2]

@palday I'm concerned about the Beacon-internal impact of requiring 1.9 here actually. Let's confirm before merging this that that's okay.

[DilumAluthge]

Instead of dropping support for old Julia versions, why not just gate this particular Arrow functionality behind a @static if Base.VERSION >= v"1.9-"? So then JSON3 will still be usable on old Julia versions, but the Arrow functionality will only be available on Julia 1.9 and later.

[palday]

@DilumAluthge The lazy loading of extensions already does that, but I was thinking about adding just such a gate to the tests.

[palday]

@quinnj gentle bump 🖤