policy: separate sourcemetaresolver utility to reusable pkg

Turn the current utility used by policy helper commands that
allows getting gateway.Client lazily into reusable package.

This is preparation for using this utility also in the policy
verification, outside of commands.

Only expose SourceMetaResolver as other methods of gateway client
are not needed atm by any callers.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

policy/tester.go

@@ -25,7 +25,7 @@ type TestOptions struct {
 	Run      string
 	Filename string
 	Root     fs.StatFS
-	Resolver *TestResolver
+	Provider *TestOptionsProvider
 }
 
 type TestSummary struct {
@@ -50,7 +50,7 @@ type testDef struct {
 	PkgPath string
 }
 
-type TestResolver struct {
+type TestOptionsProvider struct {
 	Resolve          func(context.Context, *pb.SourceOp, *gwpb.ResolveSourceMetaRequest) (*gwpb.ResolveSourceMetaResponse, error)
 	Platform         func(context.Context) (*ocispecs.Platform, error)
 	VerifierProvider PolicyVerifierProvider
@@ -286,8 +286,8 @@ func runPolicyTest(ctx context.Context, policyModules map[string]*ast.Module, te
 		return result, err
 	}
 	effectiveInput := input
-	if opts.Resolver != nil {
-		resolvedInput, ok, err := resolveTestInput(ctx, policyFiles, opts.Resolver, policyPackageModules, input, fsProvider)
+	if opts.Provider != nil {
+		resolvedInput, ok, err := resolveTestInput(ctx, policyFiles, opts.Provider, policyPackageModules, input, fsProvider)
 		if err != nil {
 			return result, err
 		}
@@ -397,7 +397,7 @@ func stateFromInput(input *Input) *state {
 	return st
 }
 
-func resolveTestInput(ctx context.Context, files []File, resolver *TestResolver, policyModules []*ast.Module, input *Input, fsProvider func() (fs.StatFS, func() error, error)) (*Input, bool, error) {
+func resolveTestInput(ctx context.Context, files []File, resolver *TestOptionsProvider, policyModules []*ast.Module, input *Input, fsProvider func() (fs.StatFS, func() error, error)) (*Input, bool, error) {
 	if resolver == nil {
 		return nil, false, nil
 	}