Change methods name

[Khadreal]

Description

Changed methods name for media library view

Fixes #779

Type of change

• Enhancement (non-breaking change which improves an existing functionality).

Is the solution different from the one proposed during the grooming?

No

Please describe in this section if there is any change to the groomed solution, and why.

Checklists

Generic development checklist

• [x] My code follows the style guidelines of this project, with adapted comments and without new warnings.
• [ ] I have added unit and integration tests that prove my fix is effective or that my feature works.
• [x] The CI passes locally with my changes (including unit tests, integration tests, linter).
• [ ] Any dependent changes have been merged and published in downstream modules.
• [ ] If applicable, I have made corresponding changes to the documentation. Provide a link to the documentation.

Test summary

• [x] I triggered all changed lines of code at least once without new errors/warnings/notices.
• [ ] I validated all Acceptance Criteria of the related issues. (If applicable, provide proof).
• [ ] I validated all test plan the QA Review asked me to.

[Khadreal]

@Miraeld I think I should assigned this https://github.com/wp-media/imagify-plugin/issues/779 to you, it seems you've already worked on it and https://github.com/wp-media/imagify-plugin/issues/778 by looking at your commits history

[Miraeld]

There is no need to re-assign it I think. From what I've seen on other PRs, we've been using next_gen notation instead of nextgen. As I needed few of these functions in an other PR, I had to rename them. I made my comment here to avoid either of us having conflicts.

[Tabrisrp]

This PR needs conflict fixed before moving forward

[Khadreal]

While resolving the conflicts I noticed that the issue #779 was created based on develop branch and deature/avif branch has few things that aren't captured in the issue. Is it safe to rename all next_gen to nextgen ? @Tabrisrp