Chore: reorganize compute function files in vortex-array

[connortsui20]

Makes sure each compute function implementation has its own file.

Note that this is a purely cosmetic change.

Yes, this is verbose, but also it's better to be consistent (and it also helps with discoverability, for example "which compute functions exist for this array type?).

[codecov]

Codecov Report

❌ Patch coverage is 78.57143% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.28%. Comparing base (4de2926) to head (3f22c1c).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
vortex-array/src/arrays/struct_/compute/take.rs	70.83%	7 Missing ⚠️
vortex-array/src/arrays/null/compute/take.rs	55.55%	4 Missing ⚠️
...ex-array/src/arrays/extension/compute/is_sorted.rs	50.00%	3 Missing ⚠️
vortex-array/src/arrays/null/compute/filter.rs	0.00%	3 Missing ⚠️
vortex-array/src/arrays/null/compute/mask.rs	0.00%	3 Missing ⚠️
vortex-array/src/arrays/null/compute/min_max.rs	0.00%	3 Missing ⚠️
...ex-array/src/arrays/struct_/compute/is_constant.rs	93.75%	1 Missing ⚠️

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