Inherit CI models from Ci::ApplicationRecord [RUN AS-IF-FOSS]

What does this MR do?

Related issue: #336426 (closed)

Introduce a new Ci::ApplicationRecord that all CI models should inherit from. The new ApplicationRecord can be used for the decomposition effort to specify the appropriate connection to the CI database.

There's a few additions in the list of models in this MR compared to the linked issue:

app/models/ci/pending_build.rb
app/models/ci/pipeline_chat_data.rb
app/models/ci/running_build.rb
ee/app/models/ci/minutes/additional_pack.rb

With the exception of Ci::PipelineChatData these all look to be recently added models, but I don't see any reason they shouldn't all be included.

Screenshots or Screencasts (strongly suggested)

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?)
• 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 #336426 (closed)