ci: Split cabal and stack work caches from regular cache

This is a first step to split up the cabal and stack caches in separate
pieces. Here we split the work folder, which just contains the
postgrest-specific build artifacts, into a separate cache.

More fine-grained caching should give us better cache hits and much
fewer upload size in the regular case, improving CI performance.

Since the work file caches are very small (about 30-40 MB) they are
cached for PRs, too. This will allow the majority of PRs, which only
change source code files, but no dependencies, to still have cached
their build files for additional commits.

.github/workflows/build.yaml

@@ -91,14 +91,12 @@ jobs:
             runs-on: ubuntu-22.04
             cache: |
               ~/.stack
-              .stack-work
             # no artifact for Linux, because we use the static build
 
           - name: MacOS
             runs-on: macos-12
             cache: |
               ~/.stack
-              .stack-work
             artifact: postgrest-macos-x64
 
           - name: Windows
@@ -106,7 +104,6 @@ jobs:
             cache: |
               ~\AppData\Roaming\stack
               ~\AppData\Local\Programs\stack
-              .stack-work
             deps: Add-Content $env:GITHUB_PATH $env:PGBIN
             artifact: postgrest-windows-x64
 
@@ -114,12 +111,19 @@ jobs:
     runs-on: ${{ matrix.runs-on }}
     steps:
       - uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29 # v4.1.6
-      - name: Stack working files cache
+      - name: Cache ~/.stack
         uses: ./.github/actions/cache-on-main
         with:
           path: ${{ matrix.cache }}
           prefix: stack
-          suffix: ${{ hashFiles('stack.yaml.lock') }}
+          suffix: ${{ hashFiles('postgrest.cabal', 'stack.yaml.lock') }}
+      - name: Cache .stack-work
+        uses: ./.github/actions/cache-on-main
+        with:
+          path: .stack-work
+          save-prs: true
+          prefix: stack-work-${{ hashFiles('postgrest.cabal', 'stack.yaml.lock') }}
+          suffix: ${{ hashFiles('main/**/*.hs', 'src/**/*.hs') }}
       - name: Install dependencies
         if: matrix.deps
         run: ${{ matrix.deps }}
@@ -169,15 +173,21 @@ jobs:
       - name: Fix caching
         run: |
           mkdir ~/.cabal
-      - name: Cache
+      - name: Cache .cabal
         uses: ./.github/actions/cache-on-main
         with:
           path: |
             ~/.cabal/packages
             ~/.cabal/store
-            dist-newstyle
           prefix: cabal-${{ matrix.ghc }}
           suffix: ${{ hashFiles('postgrest.cabal', 'cabal.project', 'cabal.project.freeze') }}
+      - name: Cache dist-newstyle
+        uses: ./.github/actions/cache-on-main
+        with:
+          path: dist-newstyle
+          save-prs: true
+          prefix: cabal-${{ matrix.ghc }}-dist-newstyle-${{ hashFiles('postgrest.cabal', 'cabal.project', 'cabal.project.freeze') }}
+          suffix: ${{ hashFiles('**/*.hs') }}
       - name: Install dependencies
         run: |
           cabal update