feat: enhance Trie data structure with added methods and tests

[sailok]

• Renamed TrieImp.java to Trie.java to be more inclined with the naming convention
• Refactored the TrieNode class from being an Inner Class to separate class with in Trie.java
• Use HashMap instead of TrieNode array in children, to incorporate all character values instead if lowercase english alphabets.
• Add countWords, startsWithPrefix and countWordsWithPrefix methods to enhance Trie capability.
• Add Test Cases to all the Trie methods.

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 83.33333% with 6 lines in your changes missing coverage. Please review.

Project coverage is 58.12%. Comparing base (6868bf8) to head (5658fa6).

Files with missing lines	Patch %	Lines
...a/com/thealgorithms/datastructures/trees/Trie.java	83.33%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5538      +/-   ##
============================================
+ Coverage     58.08%   58.12%   +0.04%     
- Complexity     3669     3676       +7     
============================================
  Files           546      546              
  Lines         15776    15796      +20     
  Branches       3000     3006       +6     
============================================
+ Hits           9164     9182      +18     
  Misses         6224     6224              
- Partials        388      390       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[siriak]

Please remove main and add JUnit tests

[siriak]

Looks good, thanks!