show correct auto complete value for nargs option in combination with flag option

[msaipraneeth]

This pull request resolves an issue in the autocompletion logic for options with nargs > 1 when combined with boolean options. Previously, autocompletion would suggest incorrect values, leading to confusion and an inconsistent user experience.

fixes #2813

• [X] Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• [X] Add or update relevant docs, in the docs folder and in code.
• [X] Add an entry in CHANGES.rst summarizing the change and linking to the issue.

[msaipraneeth]

@AndreasBackx Have we selected the correct bash branch for this PR?

[Rowlando13]

@msaipraneeth Please rebase onto stable. Thanks for your patience with changing the branch a lot.

[msaipraneeth]

@msaipraneeth Please rebase onto stable. Thanks for your patience with changing the branch a lot.

@Rowlando13 Rebased onto the stable branch. I don't see an Unreleased section in CHANGES.rst. Where should I add the update?

[Rowlando13]

Just make an unreleased section at the top and add it.

[msaipraneeth]

Just make an unreleased section at the top and add it.

@Rowlando13 Done with the changes. PR is ready for review.