Include the request number on the requests table (closes #20262)

[kshivam4781]

What

Adds the request number as its own column in the "requests" table shown on project, package, user, and group pages (the shared _requests_table.html.haml partial / bs_requests#index JSON endpoint used by all four of those controllers).

Why

Closes #20262. Package maintainers reviewing the Maintenance workflow (osc mr) currently have nothing in the table that identifies a request; they have to click "View" to learn the request number. This adds a "#" column with the request number, linked to the request, right before the existing "View" column.

Changes

• _requests_table.html.haml: add a # header cell.
• bs_requests/index.json.erb: emit a new cell per row with #<number> linking to request_show_path.
• requests_table.js: the new column is non-orderable (like the existing "View" link), so it's added to the orderable: false targets alongside the shifted "View" column index (6 -> 7).

This only touches the shared partial/JSON view, so the change applies uniformly to the project, package, user ("My Involved Requests"), and group request tables, which all render through the same webui/shared/bs_requests/index view.

Testing

I don't have a working OBS docker dev environment set up, so I wasn't able to run the RSpec/Capybara suite for this change. I did:

• Trace all four controllers (Webui::Projects::BsRequestsController, Webui::Packages::BsRequestsController, Webui::Users::BsRequestsController, Webui::Groups::BsRequestsController) to confirm they share the same _requests_table.html.haml partial and bs_requests/index.json.erb view, so one change covers all of them consistently.
• Checked the existing specs that touch this table (a_bs_requests_data_table_controller.rb's shared examples, and packages_spec.rb's Capybara test) — the new column is appended after the existing sortable columns (created/source/target/requester/type/priority stay at indices 0-5) and given no CSS class, so the existing hardcoded order: {column: 5} (priority) / column: 2 (composite target) assertions and the find('a', class: 'request_link') Capybara lookup for the "View" link are unaffected.
• Syntax-checked the compiled ERB (Ruby ERB.new(...).src + RubyVM::InstructionSequence.compile) and the JS file (node --check); manually reviewed the one-line HAML addition.

Happy to run the full suite and fix anything it turns up if a maintainer can point me at a lighter-weight way to get the specs running, or I can try to get the docker compose setup working in a follow-up.