workflows: increase tests timeout up to 25 minutes

I'm tired of tests failing due to timeout, GitHub machines are too slow.
I propose to use 25m for some time and see if we're still having
timeouting tests. If so, then we need to refactor timeouting tests,
because failure may be caused by inappropriate test design. If not, then
we may try to reduce tests timeout to 20m later.

Close #3367 along the way.

Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>

.github/workflows/tests.yml

@@ -104,7 +104,7 @@ jobs:
           cache: true
 
       - name: Write coverage profile
-        run: go test -timeout 15m -v ./... -coverprofile=./coverage.txt -covermode=atomic -coverpkg=./pkg...,./cli/...
+        run: go test -timeout 25m -v ./... -coverprofile=./coverage.txt -covermode=atomic -coverpkg=./pkg...,./cli/...
 
       - name: Upload coverage results to Codecov
         uses: codecov/codecov-action@v3
@@ -150,4 +150,4 @@ jobs:
           go-version: '${{ matrix.go_versions }}'
 
       - name: Run tests
-        run: go test -timeout 15m -v -race ./...
+        run: go test -timeout 25m -v -race ./...