Backport PR scverse#1937: Prep 1.8.1 (scverse#1938)

Co-authored-by: Isaac Virshup <[email protected]>

Start release notes for 1.9.0 (scverse#1906)

Finalize release notes (scverse#1905)

* update release notes

* Update release-latest

* Add Development processes section to 1.8 release notes

* Fix warnings from matrixplot

* Update docs/release-notes/1.8.0.rst

Co-authored-by: Giovanni Palla <[email protected]>

Prep 1.7.2 release (scverse#1785)

* Set release date
* Remove unused rubrics from release notes
* enables highly_variable_genes_seurat_v3 to accept pseudocounts (scverse#1679) 
* Add hvg change to release notes

Co-authored-by: Isaac Virshup <[email protected]>
Co-authored-by: giovp <[email protected]>

Backport PR scverse#1683: Update release notes for 1.7.1 (scverse#1686)

Co-authored-by: Isaac Virshup <[email protected]>

Backport PR scverse#1623: Release note for scverse#1583 and update re…

…lease date (scverse#1624)

Co-authored-by: Isaac Virshup <[email protected]>

updated test that works with pandas 1.2 (scverse#1584)

Add note about `twine check` to release guide

Make tests run

short version of print_versions and print_header (scverse#1373)