Implement PCA for f32 and f64

[YuhanLiin]

Addresses #232

Adds PCA impl for f32 for all BLAS backends using macros. Does not involve the Float trait.

There is currently a logic bug, as the test_explained_variance_diag and test_whitening_small tests are currently failing on f32. It might be related to the TruncateSvd code. @bytesnake any ideas?

[YuhanLiin]

I also ran the tests with BLAS backend and white_small passes, but explained_variance_diag still fails.

[bytesnake]

for explained_variance_diag this relates to rust-ml/linfa-linalg#11 when decreasing to single-precision floats we can't extract as many eigenvalues without losing coherence

[bytesnake]

the same occurs for test_whitening_small, it calculate covariance of 2x2 https://github.com/rust-ml/linfa-linalg/blob/main/src/lobpcg/svd.rs#L200

[bytesnake]

I propose first fixing first rust-ml/linfa-linalg#11 by adding the 1/5 rules to TruncatedSvd and TruncatedEig and then test again