Faster rankUpdate! method for HermitianRFP

[dmbates]

• Rewrite the rankUpdate!(C::HermitianRFP{T}, A::SparseMatrixCSC{T}, ...) method to use A.colptr directly and avoid calls to nzrange(A, j) which just add another layer of indirection.
• As part of this rewrite the levels of the second grouping factor are sorted by decreasing incidence when the reterm is generated. This concentrates more of the updates in the trapezoidal storage of C.data where linear indexing can be used.

[dmbates]

We now have the peculiar situation that the rankUpdate! method for HermitianRFP is faster on some examples than that for HermOrSym. I believe the difference is from the sorting of levels of the second grouping factor which can concentrate the positions of the updates in the upper left part of C. (This is a heuristic, not a proof.)

Should we always sort the levels of the second grouping factor when A[2, 1] is SparseMatrixCSC and A[2, 2] is dense Hermitian?

[codecov]

Codecov Report

❌ Patch coverage is 92.59259% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.92%. Comparing base (117e05c) to head (7a62f0b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/linalg/rankUpdate.jl	92.59%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #910      +/-   ##
==========================================
- Coverage   95.69%   94.92%   -0.77%     
==========================================
  Files          38       38              
  Lines        3760     3921     +161     
==========================================
+ Hits         3598     3722     +124     
- Misses        162      199      +37     

Flag	Coverage Δ
current	94.61% <92.59%> (-0.76%)	⬇️
minimum	94.82% <92.59%> (-0.77%)	⬇️
nightly	94.60% <92.59%> (-0.76%)	⬇️

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