Remove BoltDB state support

This also includes a number of significant changes to the SQLite
state made possible by removal of the legacy DB.

1. Enable database unit tests for SQLite state, with numerous
   tweaks to get tests passing. Most notable changes are to
   container removal - where we previously didn't return an error
   if there was no container to remove - and RemovePodContainers,
   which I don't think ever worked properly from my reading of
   the failures.
2. Removal of AddContainerToPod/RemoveContainerToPod. On SQLite,
   these functions are identical to AddContainer/RemoveContainer
   and there is no reason to retain duplicates.
3. Removal of SafeRewriteContainerConfig - it's identical to
   RewriteContainerConfig in SQLite, no reason to have duplicate
   entrypoints.

As an exciting side-note, this removes Podman's requirement that
containers and pods cannot share a name, which was a BoltDB
restriction only.

Signed-off-by: Matt Heon <matthew.heon@pm.me>

libpod/runtime.go

@@ -7,7 +7,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"io/fs"
 	"os"
 	"path/filepath"
 	"slices"
@@ -295,31 +294,11 @@ func getDBState(runtime *Runtime) (State, error) {
 		return nil, err
 	}
 
-	// get default boltdb path
-	baseDir := runtime.config.Engine.StaticDir
-	if runtime.storageConfig.TransientStore {
-		baseDir = runtime.config.Engine.TmpDir
-	}
-	boltDBPath := filepath.Join(baseDir, "bolt_state.db")
-
 	switch backend {
-	case config.DBBackendDefault:
-		// for backwards compatibility check if boltdb exists, if it does not we use sqlite
-		if err := fileutils.Exists(boltDBPath); err != nil {
-			if errors.Is(err, fs.ErrNotExist) {
-				// need to set DBBackend string so podman info will show the backend name correctly
-				runtime.config.Engine.DBBackend = config.DBBackendSQLite.String()
-				return NewSqliteState(runtime)
-			}
-			// Return error here some other problem with the boltdb file, rather than silently
-			// switch to sqlite which would be hard to debug for the user return the error back
-			// as this likely a real bug.
-			return nil, err
-		}
-		runtime.config.Engine.DBBackend = config.DBBackendBoltDB.String()
-		fallthrough
 	case config.DBBackendBoltDB:
-		return NewBoltState(boltDBPath, runtime)
+		return nil, fmt.Errorf("the BoltDB database backend was removed in Podman 6.0")
+	case config.DBBackendDefault:
+		fallthrough
 	case config.DBBackendSQLite:
 		return NewSqliteState(runtime)
 	default: