Combine and rename bulk edit feature specs

What does this MR do?

This MR combines and renames bulk edit feature specs for improved organisation and consistency, since they have some common code between them.

We are refactoring the issues list page (see #322755 (closed)) and need to tweak the bulk edit specs, so these changes will help make these tweaks a bit easier. The tweaks will come after this MR.

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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• I have added/updated documentation, or it's not needed. (Is documentation required?)
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• 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.

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.)
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Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team