x/authz: Add DelegateAuthorization, UndelegateAuthorization

[aleem1314]

Description

ref: #8312

---

Before we can merge this PR, please make sure that all the following items have been
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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.
• 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 #8472 (012cc59) into master (c6355fd) will increase coverage by 0.04%.
The diff coverage is 70.13%.

@@            Coverage Diff             @@
##           master    #8472      +/-   ##
==========================================
+ Coverage   61.43%   61.47%   +0.04%     
==========================================
  Files         658      659       +1     
  Lines       37768    37876     +108     
==========================================
+ Hits        23201    23283      +82     
- Misses      12143    12159      +16     
- Partials     2424     2434      +10     

Impacted Files	Coverage Δ
x/authz/types/authorization_grant.go	0.00% <0.00%> (ø)
x/authz/types/codec.go	0.00% <0.00%> (ø)
x/authz/types/generic_authorization.go	0.00% <0.00%> (ø)
x/authz/types/genesis.go	0.00% <0.00%> (ø)
x/authz/types/msgs.go	53.84% <0.00%> (ø)
x/bank/types/send_authorization.go	0.00% <0.00%> (ø)
x/authz/client/cli/tx.go	69.82% <64.00%> (-3.05%)	⬇️
x/authz/simulation/operations.go	81.11% <66.66%> (ø)
x/staking/types/authz.go	87.87% <87.87%> (ø)
x/auth/client/cli/tx_multisign.go	62.03% <100.00%> (+0.35%)	⬆️
... and 5 more

[blushi]

Looks good overall, just some nits/refactoring requests.

[aaronc]

As @blushi pointed out these are essentially the same message. So we can just include a base message and two types or something like that. Also I imagine we could cover redelegate similarly.

[blushi]

Pre-approving with a few non-blocking comments!

[aaronc]

API looks good now. Let's clean up the docs a bit

Dismissing as my change requests have been addressed

[anilcse]

lgtm