Resolve "Use Same Endpoint for HTML and JSON in OperationsController"

What does this MR do?

Refactor Operations and Environments dashboard controller which uses same action method in controller for both html and json format of the incoming request.

Screenshots or Screencasts (strongly suggested)

Operations Dashboard with the changes applied:

Environments dashboard with the changes applied:

How to setup and validate locally (strongly suggested)

Visit http://127.0.0.1:3000/-/operations/ (Operations dashboard) and select a project to add to the dashboard. Then remove the project from dashboard and verify the list again.

Visit https://127.0.0.1:3000/-/operations/environments/ (Environments dashboard) and select a project to add to the dashboard. Then remove the project from dashboard and verify the list again.

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. ([Is documentation required?](https://about.gitlab.com/handbook/engineering/ux/technical-writing/workflow/#when-documentation-is-required))
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Related to #34051 (closed)