Allow name owner to execute msg modify name

[nullpointer0x00]

Description

closes: #1536

---

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.
• 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 #1537 (e7ee050) into main (7916a9e) will increase coverage by 0.01%.
The diff coverage is 61.53%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1537      +/-   ##
==========================================
+ Coverage   61.48%   61.50%   +0.01%     
==========================================
  Files         197      197              
  Lines       25269    25319      +50     
==========================================
+ Hits        15537    15572      +35     
- Misses       8636     8651      +15     
  Partials     1096     1096              

Impacted Files	Coverage Δ
x/name/keeper/msg_server.go	38.12% <0.00%> (ø)
x/name/client/cli/tx.go	65.03% <48.78%> (-2.69%)	⬇️
x/name/simulation/operations.go	80.98% <82.35%> (+0.43%)	⬆️

[Taztingo]

LGTM

[iramiller]

Being able to leverage the same methods for gov proposals and modifications is a very nice simplification.