Add copy, lmul! and rmul! methods

[dmbates]

• Add a copy method for HermitianRFP. The other two types, TriangularRFP and CholeskyRFP, had a copy method but not Hermitian.

• Add methods for lmul! and rmul! that amount to an in-place scaling. The matrix argument in the signature is specified as AbstractRFP. Is this inefficient?

• Add a method for BLAS.syrk! with HermitianRFP.

• The choice of methods to define is influenced by what I need for the MixedModels package I will leave this as a draft PR until I finish with incorporating RFP storage in that package.

[codecov]

Codecov Report

Base: 97.04% // Head: 97.26% // Increases project coverage by +0.22% 🎉

Coverage data is based on head (4536834) compared to base (040521b).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head 4536834 differs from pull request most recent head 7545ae3. Consider uploading reports for the commit 7545ae3 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #8      +/-   ##
==========================================
+ Coverage   97.04%   97.26%   +0.22%     
==========================================
  Files           5        5              
  Lines         169      183      +14     
==========================================
+ Hits          164      178      +14     
  Misses          5        5              

Impacted Files	Coverage Δ
src/cholesky.jl	100.00% <100.00%> (ø)
src/hermitian.jl	95.65% <100.00%> (+1.90%)	⬆️
src/triangular.jl	100.00% <100.00%> (ø)
src/utilities.jl	97.43% <100.00%> (+0.46%)	⬆️

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[dmbates]

I'm happy to add other method definitions in this PR if you can think of any that you would want. As I mentioned in the description of the PR, the ones I chose to include were dictated by what I needed in another package.

[dmbates]

@andreasnoack Is it okay to merge this PR?

[andreasnoack]

Missed this PR. Yes, it looks good to me.