ci: Only save caches on main and release branches

This restores caches on all branches and pull requests, but only stores
them on the main branch and release branches. This prevents those caches
from being evicted early when we hit the 10 GB limit quickly.

.github/workflows/build.yaml

@@ -115,12 +115,11 @@ jobs:
     steps:
       - uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29 # v4.1.6
       - name: Stack working files cache
-        uses: actions/cache@0c45773b623bea8c8e75f6c82b208c3cf94ea4f9 # v4.0.2
+        uses: ./.github/actions/cache-on-main
         with:
           path: ${{ matrix.cache }}
-          key: stack-${{ runner.os }}-${{ hashFiles('stack.yaml.lock') }}
-          restore-keys: |
-            stack-${{ runner.os }}-
+          prefix: stack
+          suffix: ${{ hashFiles('stack.yaml.lock') }}
       - name: Install dependencies
         if: matrix.deps
         run: ${{ matrix.deps }}
@@ -171,15 +170,14 @@ jobs:
         run: |
           mkdir ~/.cabal
       - name: Cache
-        uses: actions/cache@0c45773b623bea8c8e75f6c82b208c3cf94ea4f9 # v4.0.2
+        uses: ./.github/actions/cache-on-main
         with:
           path: |
             ~/.cabal/packages
             ~/.cabal/store
             dist-newstyle
-          key: cabal-${{ runner.os }}-${{ matrix.ghc }}-${{ hashFiles('postgrest.cabal', 'cabal.project', 'cabal.project.freeze') }}
-          restore-keys: |
-            cabal-${{ runner.os }}-${{ matrix.ghc }}-
+          prefix: cabal-${{ matrix.ghc }}
+          suffix: ${{ hashFiles('postgrest.cabal', 'cabal.project', 'cabal.project.freeze') }}
       - name: Install dependencies
         run: |
           cabal update