Remove obsolete unit tests for number conversion and sorting algorithms

[yashksaini-coder]

✅ Closes: #454

This pull request removes several test files related to various utility functions and data structures. The most important changes include the deletion of test files for number conversions, sorting algorithms, trie data structures, and date utilities.

Removed test files:

• Tests/Number/test_binary_to_decimal.py: Removed tests for binary_to_decimal function.
• Tests/Number/test_decimal_to_binary.py: Removed tests for decimal_to_binary function.
• Tests/Number/test_decimal_to_hex.py: Removed tests for decimal_to_hex function.
• Tests/Number/test_hex_to_decimal.py: Removed tests for hex_to_decimal function.
• Tests/Number/test_octal_to_decimal.py: Removed tests for octal_to_decimal function.
• Tests/Sorting/test_selection_sort.py: Removed tests for selection_sort function.
• Tests/Tries/test_tries.py: Removed tests for Trie class and its methods.
• Tests/date_utils/test_date_utils.py: Removed tests for convert_to_iso8601 function.

Other changes:

• Tests/date_utils/__init__.py: Removed __init__.py file for date_utils package.

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@UTSAVS26 When I was working I found out some test cases can be improved and some are obsolete so they need to be removed. Kindly give level 3 for my efforts

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