feat: In r/demo/users, add ListUsersByPrefix

[jefft0]

GnoSocial uses r/demo/users to register users. A typical social app can search for other users by name, which requires a search box with partial match. The private variable name2User is an avl.Tree where the key is the user name, and avl.Tree Iterate can already iterate by start and end values. This PR has 2 commits:

1. Add a new package p/demo/avlhelpers with the function ListByteStringKeysByPrefix . Also add tests.
2. Use this in r/demo/users to add ListUsersByPrefix to return a list of user names starting from the given prefix.

For example, ListUsersByPrefix("g", 2) returns a list of 2 names with the prefix "g":

["george", "gnofan"]

In the GnoSocial demo app, we plan to use this in a search box.

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.21%. Comparing base (651f5aa) to head (21f574c).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1708      +/-   ##
==========================================
- Coverage   60.22%   60.21%   -0.01%     
==========================================
  Files         562      562              
  Lines       75038    75038              
==========================================
- Hits        45188    45182       -6     
- Misses      26476    26479       +3     
- Partials     3374     3377       +3     

Flag	Coverage Δ
contribs/gnodev	61.40% <ø> (ø)
contribs/gnofaucet	14.46% <ø> (-0.86%)	⬇️
gno.land	64.57% <ø> (ø)
gnovm	64.33% <ø> (ø)
misc/genstd	80.54% <ø> (ø)
misc/logos	19.88% <ø> (ø)
tm2	62.02% <ø> (+0.05%)	⬆️

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[jefft0]

Converted this PR to Draft while addressing the above comments and refactoring some functionality to p/demo/avlhelpers

[jefft0]

Finished updating the commits and PR description. Ready for review.

[zivkovicmilos]

Hey @jefft0, can you please merge in the latest master changes? 🙏

[jefft0]

Hey @jefft0, can you please merge in the latest master changes? 🙏

Done.

[zivkovicmilos]

Thank you for the feature 🙏

I left a comment concerning whether we want support for non-ASCII characters in the prefix

[zivkovicmilos]

@jefft0 can you please resolve the conflict in the PR, so we can merge? 🙏

[jefft0]

@jefft0 can you please resolve the conflict in the PR, so we can merge? 🙏

Hi @zivkovicmilos . I resolved the conflict. (Since I opened this PR, the master branch merged a file z_11_filetest.gno . So I just renamed my file to z_12_filetest.gno .)

[jefft0]

Since I opened this PR, r/demo/users is now pre-loaded with namespace names. So I updated z_12_filetest.gno to use a different test name that doesn't conflict. The test passes again.