CI(pg-clients): unify workflow with build-and-test (#8160)

## Problem

`pg-clients` workflow looks different from the main `build-and-test`
workflow for historical reasons (it was my very first task at Neon, and 
back then I wasn't really familiar with the rest of the CI pipelines).
This PR unifies `pg-clients` workflow with `build-and-test`

## Summary of changes
- Rename `pg_clients.yml` to `pg-clients.yml`
- Run the workflow on changes in relevant files
- Create Allure report for tests
- Send slack notifications to `#on-call-qa-staging-stream` channel
(instead of `#on-call-staging-stream`)
- Update Client libraries once we're here

test_runner/pg_clients/swift/PostgresClientKitExample/Dockerfile

@@ -1,11 +1,11 @@
-FROM swift:5.9 AS build
+FROM swift:5.10 AS build
 RUN apt-get -q update && apt-get -q install -y libssl-dev
 WORKDIR /source
 
 COPY . .
 RUN swift build --configuration release
 
-FROM swift:5.9
+FROM swift:5.10
 WORKDIR /app
 COPY --from=build /source/.build/release .
 CMD ["/app/PostgresClientKitExample"]