Add YARD annotations to remote dev shared contexts

What does this MR do and why?

• Adds missing YARD annotations to ee/spec/support/shared_contexts/remote_development/remote_development_shared_contexts.rb
• Splits one method into two to avoid having two different return types

NOTES:

• This is just a spec helper file, and we are just adding YARD annotations to avoid all the warnings in RubyMine, but it is useful because it already caught the problem with the multiple return types antipattern.
• AI was used to generate the original text, and I reviewed it and fixed some problems. There may be some minor inconsistencies with the actual types, but again this is just a spec helper file, it doesn't have to be perfect.
• If, in the future, we add Sorbet or RBS, we will have much stronger mechanisms to detect and enforce type problems. But for now, we do the best we can with YARD.

References

• Official docs recommending usage of YARD: https://docs.gitlab.com/17.9/development/code_comments/#class-and-method-documentation

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