`BLAS.geru!` added (#51951)
Closes https://github.com/JuliaLang/LinearAlgebra.jl/issues/12.
**PR Checklist**
- [x] added BLAS.geru! function in stdlib/LinearAlgebra/src/blas.jl
- [x] also added test cases for it in stdlib/LinearAlgebra/test/blas.jl
---------
Co-authored-by: Daniel Karrasch <daniel.karrasch@posteo.de>
Co-authored-by: Viral B. Shah <ViralBShah@users.noreply.github.com>
Co-authored-by: mikmoore <95002244+mikmoore@users.noreply.github.com>
Co-authored-by: Ian Butterworth <i.r.butterworth@gmail.com>
