Add/generate parentheses iterative approach

[Pr0-C0der]

Describe your change:

This PR adds the generate parentheses program using an iterative approach to the backtracking folder.
Fixes #9920

• Add an algorithm?
• Fix a bug or typo in an existing 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. To ease review, please open separate PRs for separate algorithms.
• 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".

[cclauss]

When would we want to use this algorithm?

[Pr0-C0der]

When would we want to use this algorithm?

The algorithm is used when you must generate valid parentheses combinations of length n, especially for tasks like code syntax validation and expression parsing. It's memory-efficient, safer for large n, and performs better with a reduced function call overhead, making it suitable for tasks with tight memory constraints.

[Pr0-C0der]

Hey @cclauss Can you please review this pull request and suggest any changes before merging?

[cclauss]

@tianyizheng02 Do you have an interest in this?

[Pr0-C0der]

@tianyizheng02 Can you please review it.