feat/bug: the median of the values in the array

[raisadz]

Is your feature request related to a problem?

Could you please consider implementing the median function of the values in the array similar to the mean function https://ibis-project.org/reference/expression-collections#ibis.expr.types.arrays.ArrayValue.means

import ibis
   ...: >>> ibis.options.interactive = True
   ...: >>> t = ibis.memtable({"arr": [[1, 2, 3], [None, 6], [None], [], None]})
   ...: >>> t.mutate(x=t.arr.medians())

AttributeError: 'ArrayColumn' object has no attribute 'medians'

It also looks like if I try arr.median() it outputs the following which doesn't look right:

import ibis
   ...: >>> ibis.options.interactive = True
   ...: >>> t = ibis.memtable({"arr": [[1, 2, 3], [None, 6], [None], [], None]})
   ...: >>> t.mutate(x=t.arr.median())
Out[1]: 
┏━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━┓
┃ arr                  ┃ x                    ┃
┡━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━┩
│ array<int64>         │ array<int64>         │
├──────────────────────┼──────────────────────┤
│ [1, 2, ... +1]       │ [1, 2, ... +1]       │
│ [None, 6]            │ [1, 2, ... +1]       │
│ [None]               │ [1, 2, ... +1]       │
│ []                   │ [1, 2, ... +1]       │
│ NULL                 │ [1, 2, ... +1]       │
└──────────────────────┴──────────────────────┘

What is the motivation behind your request?

Describe the solution you'd like

import ibis
   ...: >>> ibis.options.interactive = True
   ...: >>> t = ibis.memtable({"arr": [[1, 2, 3], [None, 6], [None], [], None]})
   ...: >>> t.mutate(x=t.arr.medians())

┏━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━┓
┃ arr                  ┃ x       ┃
┡━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━┩
│ array<int64>         │ float64 │
├──────────────────────┼─────────┤
│ [1, 2, ... +1]       │     2.0 │
│ [None, 6]            │     6.0 │
│ [None]               │    NULL │
│ []                   │    NULL │
│ NULL                 │    NULL │
└──────────────────────┴─────────┘

What version of ibis are you running?

11.0.0

What backend(s) are you using, if any?

DuckDB

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