fix: Fixed passing of missing backend argument in few function calls

[Sai-Suraj-27]

PR Description

In few files, in some of the function calls, the mandatory key-word argument backend is missing:
like in the following cases:
https://github.com/unifyai/ivy/blob/b5422a79808a860068e63d11233b0c0a2461d30f/ivy_tests/test_ivy/test_frontends/test_torch/test_tensor.py#L10194
https://github.com/unifyai/ivy/blob/b5422a79808a860068e63d11233b0c0a2461d30f/ivy_tests/test_ivy/test_frontends/test_torch/test_tensor.py#L10195

From the definition of flatten_and_to_np I see that backend is a mandatory key-word argument.
https://github.com/unifyai/ivy/blob/b5422a79808a860068e63d11233b0c0a2461d30f/ivy_tests/test_ivy/helpers/function_testing.py#L2408
So, I see that this argument is missing at few places when calling helpers.flatten_and_to_np() I think at all these places backend=backend_fw should be passed.

Related Issue

Closes #27110

Checklist

• Did you add a function?
• Did you add the tests?
• Did you run your tests and are your tests passing?
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[Sai-Suraj-27]

@vedpatwardhan this is similar to this PR (#27133) that you reviewed which we discussed here (#27109). Please look into this, and a similar one (#27808) thank you.

[vedpatwardhan]

lgtm! Feel free to merge the PR @NiteshK84, thanks @Sai-Suraj-27 😄