all: clean up the configs for pruner and snapshotter (#22396)

This PR cleans up the configurations for pruner and snapshotter by passing a config struct.

And also, this PR disables the snapshot background generation if the chain is opened in "read-only" mode. The read-only mode is necessary in some cases. For example, we have a list of commands to open the etheruem node in "read-only" mode, like export-chain. In these cases, the snapshot background generation is non expected and should be banned explicitly.

cmd/utils/flags.go

@@ -2198,6 +2198,9 @@ func MakeChain(ctx *cli.Context, stack *node.Node) (*core.BlockChain, ethdb.Data
 	if !ctx.Bool(SnapshotFlag.Name) {
 		cache.SnapshotLimit = 0 // Disabled
 	}
+	// Disable snapshot generation/wiping by default
+	cache.SnapshotNoBuild = true
+
 	if ctx.IsSet(CacheFlag.Name) || ctx.IsSet(CacheTrieFlag.Name) {
 		cache.TrieCleanLimit = ctx.Int(CacheFlag.Name) * ctx.Int(CacheTrieFlag.Name) / 100
 	}
@@ -2206,7 +2209,6 @@ func MakeChain(ctx *cli.Context, stack *node.Node) (*core.BlockChain, ethdb.Data
 	}
 	vmcfg := vm.Config{EnablePreimageRecording: ctx.Bool(VMEnableDebugFlag.Name)}
 
-	// TODO(rjl493456442) disable snapshot generation/wiping if the chain is read only.
 	// Disable transaction indexing/unindexing by default.
 	chain, err := core.NewBlockChain(chainDb, cache, gspec, nil, engine, vmcfg, nil, nil)
 	if err != nil {