Update doc/release-process.md

Summary:
Move version number bump step to directly after git tag
Move IBD step to after Gitian Build
Add "with and without" assumevalid=0 and checkpoints=0 for IBD
Make capitalization of "Gitian Build" consistent
Move AUR/PPA/Docker builder notification earlier
Move Qt test step earlier, and expand description

Test Plan:
Release manager verify that checklist corresponds to the
order he actually follows during a release.

Reviewers: jasonbcox, #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D3603