Performance improvements for Unitful conversion

[Deduction42]

Fix for issue #139, major (~500x) performance improvements when converting from Unitful to DynamicUnits, minor improvements to reverse case.

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Benchmark Results

	main	2601bdd79af521...	main/2601bdd79af521...
Quantity/creation/Quantity(x)	2.79 ± 0 ns	3.11 ± 0.01 ns	0.9
Quantity/creation/Quantity(x, length=y)	3.42 ± 0.01 ns	3.11 ± 0.001 ns	1.1
Quantity/with_numbers/*real	3.11 ± 0.01 ns	3.11 ± 0.001 ns	1
Quantity/with_numbers/^int	8.37 ± 2.5 ns	8.68 ± 2.5 ns	0.964
Quantity/with_numbers/^int * real	8.05 ± 2.2 ns	8.37 ± 2.2 ns	0.963
Quantity/with_quantity/+y	4.04 ± 0.01 ns	4.04 ± 0.01 ns	1
Quantity/with_quantity//y	3.11 ± 0.001 ns	3.42 ± 0.01 ns	0.909
Quantity/with_self/dimension	2.79 ± 0 ns	3.1 ± 0.01 ns	0.9
Quantity/with_self/inv	3.11 ± 0.001 ns	3.41 ± 0.01 ns	0.912
Quantity/with_self/ustrip	2.79 ± 0.01 ns	3.1 ± 0.01 ns	0.903
QuantityArray/broadcasting/multi_array_of_quantities	0.146 ± 0.0017 ms	0.143 ± 0.0012 ms	1.02
QuantityArray/broadcasting/multi_normal_array	0.0528 ± 0.0029 ms	0.0528 ± 0.0017 ms	0.999
QuantityArray/broadcasting/multi_quantity_array	0.157 ± 0.00077 ms	0.157 ± 0.00075 ms	0.999
QuantityArray/broadcasting/x^2_array_of_quantities	24 ± 2 μs	23.8 ± 1.6 μs	1.01
QuantityArray/broadcasting/x^2_normal_array	4.14 ± 1.5 μs	4.26 ± 1 μs	0.972
QuantityArray/broadcasting/x^2_quantity_array	7.13 ± 27 μs	7.11 ± 28 μs	1
QuantityArray/broadcasting/x^4_array_of_quantities	0.0844 ± 0.00056 ms	0.0814 ± 0.00075 ms	1.04
QuantityArray/broadcasting/x^4_normal_array	0.0498 ± 0.00018 ms	0.0498 ± 0.00019 ms	1
QuantityArray/broadcasting/x^4_quantity_array	0.0499 ± 0.0002 ms	0.0499 ± 0.00022 ms	1
time_to_load	0.143 ± 0.0012 s	0.144 ± 0.0019 s	0.992

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR. Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).

[MilesCranmer]

Seems to be failing the tests?

[Deduction42]

Is it passing the tests now? I see a green checkmark on "Benchmark a pull request" workflow. I has one workflow awaiting approval. Is there something else I need to look at for the tests?

[Deduction42]

Okay, I think I know what happened. I made some changes to Main on my side and I didn't know that the pull request tracked the current version of my repo. I revered those changes so that only the changes we discussed were made. Sorry about that.

[Deduction42]

I ran the tests locally and they passed. Hopefully it will work now on your end.

[MilesCranmer]

Thanks for the PR!

[Deduction42]

No problem!