Use upstream sklearn PCA if possible

[flying-sheep]

this PR

• moves _pca_with_sparse behind a check for scipy <1.4, which has @ivirshup’s port of that code https://github.com/scikit-learn/scikit-learn/pull/18689

• simplifies our logic around which parameters lead to which dispatch

  this makes it useful to get this in before #3263

• throws a warning when people use the lobpcg solver, since the closure of https://github.com/scikit-learn/scikit-learn/issues/12794#issuecomment-2118064158 makes it unlikely that we can count on that getting in any time soon

[codecov[bot]]

Codecov Report

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

Project coverage is 77.04%. Comparing base (48706ca) to head (1a1a396).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3267 +/- ## ========================================== + Coverage 76.74% 77.04% +0.29% ========================================== Files 109 110 +1 Lines 12466 12470 +4 ========================================== + Hits 9567 9607 +40 + Misses 2899 2863 -36 ``` | [Flag](https://app.codecov.io/gh/scverse/scanpy/pull/3267/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse) | Coverage Δ | | |---|---|---| | [](https://app.codecov.io/gh/scverse/scanpy/pull/3267/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse) | `77.04% <100.00%> (+0.29%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files with missing lines](https://app.codecov.io/gh/scverse/scanpy/pull/3267?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse) | Coverage Δ | | |---|---|---| | [src/scanpy/preprocessing/\_pca/\_\_init\_\_.py](https://app.codecov.io/gh/scverse/scanpy/pull/3267?src=pr&el=tree&filepath=src%2Fscanpy%2Fpreprocessing%2F_pca%2F__init__.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse#diff-c3JjL3NjYW5weS9wcmVwcm9jZXNzaW5nL19wY2EvX19pbml0X18ucHk=) | `93.71% <100.00%> (ø)` | | | [src/scanpy/preprocessing/\_pca/\_compat.py](https://app.codecov.io/gh/scverse/scanpy/pull/3267?src=pr&el=tree&filepath=src%2Fscanpy%2Fpreprocessing%2F_pca%2F_compat.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse#diff-c3JjL3NjYW5weS9wcmVwcm9jZXNzaW5nL19wY2EvX2NvbXBhdC5weQ==) | `100.00% <100.00%> (ø)` | | | [src/scanpy/preprocessing/\_simple.py](https://app.codecov.io/gh/scverse/scanpy/pull/3267?src=pr&el=tree&filepath=src%2Fscanpy%2Fpreprocessing%2F_simple.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse#diff-c3JjL3NjYW5weS9wcmVwcm9jZXNzaW5nL19zaW1wbGUucHk=) | `90.64% <ø> (+2.00%)` | :arrow_up: | ... and [9 files with indirect coverage changes](https://app.codecov.io/gh/scverse/scanpy/pull/3267/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scverse)