Move date time picker component to vue_shared (2)

What does this MR do?

This MR moves the <date-time-picker> component to vue_shared so it can be reused by other stages and parts of the application.

Additionally some of the CSS used is clean up so the component can be easily ported to other parts of the application.

Screenshots

Slight change in spacing was done in order to move away from custom css and into utility classes. Please note the spaces between the 2 columns and the bottom of the component.

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Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• 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

Required by #197879 (closed)