feat: bypass min fee check for custom message types (backport #1447)

[mergify]

This is an automatic backport of pull request #1447 done by Mergify.
Cherry-pick of 0e94267 has failed:

On branch mergify/bp/release/v7.0.x/pr-1447
Your branch is up to date with 'origin/release/v7.0.x'.

You are currently cherry-picking commit 0e94267.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	renamed:    app/ante_handler.go -> ante/ante.go
	new file:   ante/ante_test.go
	new file:   ante/fee.go
	new file:   ante/fee_test.go
	modified:   app/app.go
	modified:   app/helpers/test_helpers.go
	new file:   app/params/config.go
	modified:   cmd/gaiad/cmd/root.go
	modified:   cmd/gaiad/cmd/root_test.go
	modified:   cmd/gaiad/cmd/testnet.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md
	both modified:   docs/governance/formatting.md
	both modified:   docs/governance/params-change/Crisis.md
	both modified:   docs/governance/params-change/Slashing.md
	both modified:   docs/governance/params-change/param-index.md
	both modified:   docs/governance/proposals/2021-09-hub-ibc-router/README.md
	both modified:   docs/governance/state-of-cosmos-governance-2021.md
	both modified:   docs/gtm-interchain.md
	both modified:   docs/hub-tutorials/upgrade-node.md
	both modified:   docs/launch/blog-2-en.md
	both modified:   docs/migration/cosmoshub-3.md
	both modified:   docs/migration/cosmoshub-3[ES_es].md
	both modified:   docs/migration/cosmoshub-3[KR_kr].md
	both modified:   docs/validators/validator-faq.md
	both modified:   docs/validators/validator-setup.md
	both modified:   docs/zh/launch/blog-2-cn.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release/v7.0.x@0664d9e). Click here to learn what that means.
The diff coverage is n/a.

@@                Coverage Diff                @@
##             release/v7.0.x    #1457   +/-   ##
=================================================
  Coverage                  ?   15.68%           
=================================================
  Files                     ?       10           
  Lines                     ?     1371           
  Branches                  ?        0           
=================================================
  Hits                      ?      215           
  Misses                    ?     1145           
  Partials                  ?       11           

[alexanderbez]

Conflicts resolved @okwme -- sorry for the delay. I don't do a good job of checking Gaia GH notifications