Update `sha_mismatch.vue` to match new designs
As part of the restructuring the merge request widget we will need to create a new sha_mismatch.vue component to match the designs below.
This should against be relatively straight forward as its mainly just copy.
We may need to update the get_state_key.js if statement to show this state (https://gitlab.com/gitlab-org/gitlab/-/blob/2d3735bd61f6343faa7e6462923ac2d389eec32d/app/assets/javascripts/vue_merge_request_widget/stores/get_state_key.js#L24) as currently it can be possible to be in the ready_to_merge.vue state and have a SHA mismatch.
Component
Designs
