[improve][client] Replace NameUtil#generateRandomName with RandomStringUtils#randomAlphanumeric

[geniusjoe]

Main Issue: apache/pulsar-client-go#1297
Relative #23577

Motivation

According to #23577 (comment), currently NameUtil#generateRandomName() is only used in just few cases. Maybe we could use org.apache.commons.lang3.RandomStringUtils#randomAlphanumeric(int) to replace this class for better readability and code structure.

Modifications

Based on #23577 (comment) intention:
Remove NameUtil completely and use Commons Lang3's org.apache.commons.lang3.RandomStringUtils#randomAlphanumeric(int) method with the parameter 5 to create a random string of 5 characters.

Verifying this change

This change added tests and can be verified as follows:
org.apache.pulsar.client.impl.ConsumerImplTest#testAutoGenerateConsumerName

Does this pull request potentially affect one of the following parts:

• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
  Default consumer name generating rule will be changed from [a-f0-9]{5} to [a-zA-Z0-9]{5}.
• The threading model
• The binary protocol
• The REST endpoints
• The admin CLI options
• The metrics
• Anything that affects deployment

Documentation

• doc
• doc-required
• doc-not-needed
• doc-complete

Matching PR in forked repository

PR in forked repository:

[lhotari]

LGTM

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.36%. Comparing base (bbc6224) to head (670989f).
Report is 767 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #23645      +/-   ##
============================================
+ Coverage     73.57%   74.36%   +0.78%     
- Complexity    32624    34999    +2375     
============================================
  Files          1877     1943      +66     
  Lines        139502   147201    +7699     
  Branches      15299    16240     +941     
============================================
+ Hits         102638   109462    +6824     
- Misses        28908    29309     +401     
- Partials       7956     8430     +474     

Flag	Coverage Δ
inttests	27.50% <80.00%> (+2.91%)	⬆️
systests	24.30% <60.00%> (-0.02%)	⬇️
unittests	73.74% <100.00%> (+0.90%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...va/org/apache/pulsar/client/impl/ConsumerBase.java	75.68% <100.00%> (+1.55%)	⬆️
...va/org/apache/pulsar/client/impl/ConsumerImpl.java	80.27% <100.00%> (+2.70%)	⬆️
...he/pulsar/client/impl/MultiTopicsConsumerImpl.java	77.87% <100.00%> (+0.15%)	⬆️

... and 665 files with indirect coverage changes