Fix remaining “merge blocked” states in MR merge widget

Follow-up from !71721 (comment 702513034)

There are some “merge blocked” states that we haven't covered yet.

State Screenshot Notes
Checking image Misaligned and “error” message should be using the default text color.
SHA mismatch image Same as above
Rebase image Rebase button should be after text. See design specs
Conflicts image Merge button should not be visible and “error” message should be using the default text color. See design specs
Pipeline must succeed image Same as above
Pipeline blocked image Same as above
Draft image Same as above
Unresolved threads image Same as above
Missing approvals Missing_required_approvals
Project archived Project_is_archived
Has denied licenses Has_denied_licenses
Source or target branch is missing Source_or_target_branch_is_missing
Using a secondary Geo node Using_a_secondary_Geo_node
Blocked by another MR Blocked_by_another_MR
Edited by Pedro Moreira da Silva