ci: upgrade benchstat actions, go version -> 1.21.x

* closes #759

Squashed commit of the following:

commit 3d94ee14aeaf9a868dbeed4b65f90ccdda1f08d6
Author: Mohammed Sohail <[email protected]>
Date:   Thu Dec 7 11:49:07 2023 +0300

    ci: upgrade benchstat actions, go version -> 1.21.x

commit 129e225
Author: angshumukherjee100 <[email protected]>
Date:   Sun Oct 8 11:20:43 2023 +0530

    (workflow): bump go version to 1.18 in benchstat

.github/workflows/benchstat.yml

@@ -11,20 +11,20 @@ jobs:
     runs-on: ubuntu-latest
     services:
       redis:
-        image: redis
+        image: redis:7
         ports:
           - 6379:6379
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v4
         with:
-          go-version: 1.16.x
+          go-version: 1.21.x
       - name: Benchmark
         run: go test -run=^$ -bench=. -count=5 -timeout=60m ./... | tee -a new.txt
       - name: Upload Benchmark
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v3
         with:
           name: bench-incoming
           path: new.txt
@@ -33,22 +33,22 @@ jobs:
     runs-on: ubuntu-latest
     services:
       redis:
-        image: redis
+        image: redis:7
         ports:
           - 6379:6379
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           ref: master
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v4
         with:
-          go-version: 1.15.x
+          go-version: 1.21.x
       - name: Benchmark
         run: go test -run=^$ -bench=. -count=5 -timeout=60m ./... | tee -a old.txt
       - name: Upload Benchmark
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v3
         with:
           name: bench-current
           path: old.txt
@@ -58,25 +58,25 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v4
         with:
-          go-version: 1.15.x
+          go-version: 1.21.x
       - name: Install benchstat
         run: go get -u golang.org/x/perf/cmd/benchstat
       - name: Download Incoming
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v3
         with:
           name: bench-incoming
       - name: Download Current
-        uses: actions/download-artifact@v2
+        uses: actions/download-artifact@v3
         with:
           name: bench-current
       - name: Benchstat Results
         run: benchstat old.txt new.txt | tee -a benchstat.txt
       - name: Upload benchstat results
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v3
         with:
           name: benchstat
           path: benchstat.txt