Faster sieve_of_eratosthenes.py implementation & memo optimized

[Sumit210106]

Describe your change:

This PR optimizes the existing prime_sieve implementation:

• Skips all even numbers after 2 to reduce iterations.
• Marks only odd multiples starting from i*i.
• Collects primes efficiently after marking.
• Preserves existing doctests and interface.
• Improves runtime and keeps memory usage low.

This makes the algorithm faster while keeping outputs identical to the previous version.

• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- doctests preserved.
• Add an algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".