ci: migrate runs-on to Twilio runner labels

Repoints runs-on to the standard Twilio runner labels for this repo.
Unmapped runners (macOS, matrix expressions, etc.) left as-is.

Author: charlottestjohn

.github/workflows/benchmark.yml

@@ -12,7 +12,7 @@ jobs:
           - master
           - ${{ github.sha }}
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-large
 
     steps:
       - name: Setup Go
@@ -37,7 +37,7 @@ jobs:
 
   benchstat:
     needs: [benchmark]
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-large
 
     steps:
       - name: Setup Go

.github/workflows/test.yml

@@ -12,7 +12,7 @@ jobs:
           - "1.23"
           - "1.24"
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-latest-large
 
     steps:
       - uses: actions/checkout@v2