config: backport the rename of fastsync to blocksync (#9259)

This is largely a cherry pick of #6755 with some additional fixups added where detected. 
This change moves the blockchain package to a package called blocksync. Additionally, it renames the relevant uses of the term `fastsync` to `blocksync`.

closes: #9227 

#### PR checklist

- [ ] Tests written/updated, or no tests needed
- [x] `CHANGELOG_PENDING.md` updated, or no changelog entry needed
- [x] Updated relevant documentation (`docs/`) and code comments, or no
      documentation updates needed

test/e2e/runner/setup.go

@@ -284,7 +284,11 @@ func MakeConfig(node *e2e.Node) (*config.Config, error) {
 		cfg.Mempool.Version = node.Mempool
 	}
 
-	cfg.FastSyncMode = node.FastSync
+	if node.BlockSync == "" {
+		cfg.BlockSyncMode = false
+	} else {
+		cfg.BlockSync.Version = node.BlockSync
+	}
 
 	if node.StateSync {
 		cfg.StateSync.Enable = true