refactor(rust/sedona-functions): Let ST_Affine keep scalar args unexpanded

[yutannihilation]

This tries to address #504 (comment)

In the case of a scalar argument, DAffine2Iterator and DAffine3Iterator now hold Option<f64> instead of expanded array. I think this needs to be benchmarked to see if this change is worth, so I set this pull request as a draft.

[yutannihilation]

I finally added some benchmarks. It seems the result shows this doesn't make difference..., so let's keep the current implementation!

Current main branch

---------------------------------------------------------------------------------------------- benchmark: 3 tests ---------------------------------------------------------------------------------------------
Name (time in ms)                                     Min               Max              Mean            StdDev            Median               IQR            Outliers       OPS            Rounds  Iterations
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
test_st_affine_2d[array-SedonaDBSingleThread]      2.7364 (1.0)      2.8716 (1.01)     2.7668 (1.0)      0.0211 (1.36)     2.7627 (1.0)      0.0243 (1.15)        81;16  361.4301 (1.0)         353           1
test_st_affine_2d[mixed-SedonaDBSingleThread]      2.7562 (1.01)     2.8516 (1.0)      2.7835 (1.01)     0.0155 (1.0)      2.7828 (1.01)     0.0211 (1.0)          98;7  359.2600 (0.99)        356           1
test_st_affine_2d[scalar-SedonaDBSingleThread]     2.7736 (1.01)     3.0790 (1.08)     2.8028 (1.01)     0.0317 (2.04)     2.7974 (1.01)     0.0235 (1.12)        14;12  356.7848 (0.99)        281           1
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Legend:
  Outliers: 1 Standard Deviation from Mean; 1.5 IQR (InterQuartile Range) from 1st Quartile and 3rd Quartile.
  OPS: Operations Per Second, computed as 1 / Mean

This branch

---------------------------------------------------------------------------------------------- benchmark: 3 tests ---------------------------------------------------------------------------------------------
Name (time in ms)                                     Min               Max              Mean            StdDev            Median               IQR            Outliers       OPS            Rounds  Iterations
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
test_st_affine_2d[array-SedonaDBSingleThread]      2.7400 (1.0)      2.8557 (1.01)     2.7755 (1.0)      0.0192 (1.33)     2.7730 (1.0)      0.0241 (1.25)        103;3  360.2989 (1.0)         346           1
test_st_affine_2d[mixed-SedonaDBSingleThread]      2.7645 (1.01)     2.8371 (1.0)      2.7950 (1.01)     0.0144 (1.0)      2.7936 (1.01)     0.0193 (1.0)         102;4  357.7813 (0.99)        351           1
test_st_affine_2d[scalar-SedonaDBSingleThread]     2.7962 (1.02)     3.1533 (1.11)     2.8457 (1.03)     0.0622 (4.32)     2.8209 (1.02)     0.0381 (1.98)        12;12  351.4086 (0.98)         92           1
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Legend:
  Outliers: 1 Standard Deviation from Mean; 1.5 IQR (InterQuartile Range) from 1st Quartile and 3rd Quartile.
  OPS: Operations Per Second, computed as 1 / Mean