Add changelog commits from 0.14.0

[redshiftzero]

Status

Ready for review

Description of Changes

Towards #4550

Changes proposed in this pull request:

• Merges changelog commits back to develop
• Bump to 1.0.0~rc1

Testing

Ensure all commits are properly backported from the release branch

Deployment

Already in prod

Checklist

If you made changes to the server application code:

• Linting (make lint) and tests (make -C securedrop test) pass in the development container

If you made changes to securedrop-admin:

• Linting and tests (make -C admin test) pass in the admin development container

If you made changes to the system configuration:

• Configuration tests pass

If you made non-trivial code changes:

• I have written a test plan and validated it for this PR

If you made changes to documentation:

• Doc linting (make docs-lint) passed locally

[codecov-io]

Codecov Report

Merging #4616 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #4616   +/-   ##
========================================
  Coverage    82.63%   82.63%           
========================================
  Files           45       45           
  Lines         3122     3122           
  Branches       337      337           
========================================
  Hits          2580     2580           
  Misses         456      456           
  Partials        86       86

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[emkll]

Rebased on latest develop and appended 0c8af94 to bump version to 1.0.0~rc1. This should now be ready for re-review.

@redshiftzero 's changes look good to me, but since I've appended 0c8af94 to bump version, could another maintainer please review these changes?

[zenmonkeykstop]

LGTM based on diff review!