rename configuration parameters to use the new blocksync nomenclature (#6896)

The 0.35 release cycle renamed the 'fastsync' functionality to 'blocksync'. This change brings the configuration parameters in line with that change. Namely, it updates the configuration file `[fastsync]` field to be `[blocksync]` and changes the command line flag and config file parameters `--fast-sync` and `fast-sync` to `--enable-block-sync` and `enable-block-sync` respectively.

Error messages were added to help users encountering these changes be able to quickly make the needed update to their files/scripts.

When using the old command line argument for fast-sync, the following is printed

```
./build/tendermint start --proxy-app=kvstore --consensus.create-empty-blocks=false --fast-sync=false
ERROR: invalid argument "false" for "--fast-sync" flag: --fast-sync has been deprecated, please use --enable-block-sync
```

When using one of the old config file parameters, the following is printed:
```
./build/tendermint start --proxy-app=kvstore --consensus.create-empty-blocks=false
ERROR: error in config file: a configuration parameter named 'fast-sync' was found in the configuration file. The 'fast-sync' parameter has been renamed to 'enable-block-sync', please update the 'fast-sync' field in your configuration file to 'enable-block-sync'
```

test/e2e/runner/setup.go

@@ -297,7 +297,7 @@ func MakeConfig(node *e2e.Node) (*config.Config, error) {
 	}
 
 	if node.BlockSync == "" {
-		cfg.FastSyncMode = false
+		cfg.BlockSync.Enable = false
 	} else {
 		cfg.BlockSync.Version = node.BlockSync
 	}