Flag value doesn't accept string literals or escape sequences

**Versions**
WorldEdit version:
WorldEdit version 7.2.5
https://github.com/EngineHub/WorldEdit/
------------------ Platforms ------------------
* Bukkit-Official(7.2.5+57d5ac9)

---------------- Capabilities ----------------
GAME_HOOKS: Bukkit-Official
CONFIGURATION: Bukkit-Official
USER_COMMANDS: Bukkit-Official
PERMISSIONS: Bukkit-Official
WORLDEDIT_CUI: Bukkit-Official
WORLD_EDITING: Bukkit-Official

WorldGuard version:
WorldGuard 7.0.4
http://www.enginehub.org
----------- Platforms -----------
* Bukkit-Official (7.0.4+f7ff984)

Platform version:
This server is running Paper version git-Paper-744 (MC: 1.16.5) (Implementing API version 1.16.5-R0.1-SNAPSHOT)

**Describe the bug**
Worldguard doesn't allow for escape sequences or string literals (quotes) in the flag value argument(s). One of the consequences is that you can't set a region with the greeting "foo -w bar" or something similar.

**To Reproduce**
1. /rg define dummy
2. /rg flag -w world dummy greeting The -w option can't be used here, because flag values don't parse properly!

**Expected behavior**
Expected the commands to succeed. Instead, it says "Value flag 'w' already given" on the second command.

**Additional context**
The solution to this issue might be to build a check if the arg length is equal to 3, to then get the arg value from the CommandContext through the parsed arguments.
https://github.com/EngineHub/WorldGuard/blob/master/worldguard-core/src/main/java/com/sk89q/worldguard/commands/region/RegionCommands.java#L500