docs: improve running e2e and regression tests docs
Created by: valerybugakov
Context
This PR updates "Running end-to-end tests" docs based on recent improvements made in the sg CLI.
Closes #40256 (closed) Thanks, @courier-new, for bringing this up!
Changes
- Renamed sg
frontendtest toclientto be consistent with naming in other places and avoid confusion with thefrontendbackend service. - Moved most of
preamblecontents fromsg.config.yamlto docs and added docs links to preambles. - Added
sg test regressioncommand to thesg.config.yaml. - Updated
Running end-to-end testsdocs. - Added
Running regression testsdocs. - Made
LOG_STATUS_MESSAGESandNO_CLEANUPenv variables optional andtrueby default.
Test plan
Run e2e and regression tests locally using the updated documentation.