Merge branch 'cells_1_0_development_faq' into 'master'

Add FAQ for cluster-wide feature for Cells 1.0

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/147741



Merged-by: Lorena Ciutacu <lciutacu@gitlab.com>
Approved-by: Kamil Trzciński <ayufan@ayufan.eu>
Approved-by: Lorena Ciutacu <lciutacu@gitlab.com>
Reviewed-by: Kamil Trzciński <ayufan@ayufan.eu>
Reviewed-by: Lorena Ciutacu <lciutacu@gitlab.com>
Co-authored-by: Thong Kuah <tkuah@gitlab.com>