Allow generate-only to fully operate offline

[alexanderbez]

#4234 did not fully prohibit --generate-only from working offline. This PR forces --generate-only to work offline and removes a lot of cruft from the tx generation process all-together.

closes: #4305

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• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry: clog add [section] [stanza] [message]

• rereviewed Files changed in the github PR explorer

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For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #4306 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #4306      +/-   ##
==========================================
- Coverage   59.12%   59.11%   -0.01%     
==========================================
  Files         217      217              
  Lines       14605    14589      -16     
==========================================
- Hits         8635     8625      -10     
+ Misses       5332     5326       -6     
  Partials      638      638

[fedekunze]

ACK