.github/workflows: run go test -race for all packages (#3848)

Concurrency tests in the root package, text/v2, vector, internal/thread,
internal/hook, internal/gamepaddb, exp/textinput and exp/vmhost only
catch a data race under the race detector. Run go test -race on ./...
with -p=1, like the plain Linux step, in one Linux cell with the newest
Go, as the races are not platform specific and every Go version in the
matrix compiles the same code.

Closes #3569

.github/workflows/test.yml

@@ -129,6 +129,11 @@ jobs:
         run: |
           go test -shuffle=on -v -p=1 ./...
 
+      - name: go test -race (Linux)
+        if: runner.os == 'Linux' && matrix.go == '1.27.x'
+        run: |
+          go test -race -shuffle=on -v -p=1 ./...
+
       - name: go test (Linux 386)
         if: runner.os == 'Linux'
         run: |