bump identifier maximum to 64 characters

[colin-axner]

Description

Increased identifier limit to 64 characters

closes: #XXXX

---

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 #6812 into master will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6812      +/-   ##
==========================================
+ Coverage   61.17%   61.21%   +0.04%     
==========================================
  Files         415      510      +95     
  Lines       25171    31531    +6360     
==========================================
+ Hits        15399    19303    +3904     
- Misses       8493    10733    +2240     
- Partials     1279     1495     +216     

[ethanfrey]

Looks good to me.

Thanks for upping this limit

[cwgoes]

utACK

[fedekunze]

ACK. Pending test fixes

[adizere]

In the ibc-rs ICS24 implementation we're assuming a limit of 20 characters on any identifier. Not sure where this limit came from. Ideally, implementation updates should be downstream of cosmos/ics (canonical) updates. @cwgoes will there also be an update to ICS024?

[cwgoes]

In the ibc-rs ICS24 implementation we're assuming a limit of 20 characters on any identifier. Not sure where this limit came from. Ideally, implementation updates should be downstream of cosmos/ics (canonical) updates. @cwgoes will there also be an update to ICS024?

At the moment, the spec does not limit identifier length, because it isn't relevant to protocol safety - the 20 character limit was probably from a previous SDK version - but I can add this information to the spec if it would be helpful.

cosmos/ibc#451