Rename auth module to authn

[aleem1314]

Description

ref: #7615

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• 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.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #8447 (1c553bf) into master (2e9fd04) will not change coverage.
The diff coverage is 88.88%.

@@           Coverage Diff           @@
##           master    #8447   +/-   ##
=======================================
  Coverage   61.49%   61.49%           
=======================================
  Files         651      651           
  Lines       37250    37250           
=======================================
  Hits        22906    22906           
  Misses      11942    11942           
  Partials     2402     2402           

Impacted Files	Coverage Δ
client/tx/legacy.go	0.00% <ø> (ø)
client/tx/tx.go	29.09% <ø> (ø)
simapp/app.go	85.33% <ø> (ø)
simapp/genesis_account.go	100.00% <ø> (ø)
simapp/simd/cmd/genaccounts.go	62.76% <ø> (ø)
simapp/simd/cmd/root.go	61.47% <ø> (ø)
simapp/state.go	0.00% <ø> (ø)
simapp/test_helpers.go	0.50% <ø> (ø)
testutil/network/network.go	89.95% <ø> (ø)
testutil/network/util.go	71.02% <ø> (ø)
... and 83 more

[fedekunze]

See #7615 (comment)

[tac0turtle]

Closing the pr due to staleness. Please open a new or with the same branch completed. Let's get this work merged if it has been agreed on