[Feature] Add Experience Gain Toggle. (#2676)

* [Feature] Add Experience Gain Toggle.

# Perl
- Add `$client->IsEXPEnabled()`.
- Add `$client->SetEXPEnabled(is_exp_enabled)`.

# Lua
- Add `client:IsEXPEnabled()`.
- Add `client:SetEXPEnabled(is_exp_enabled)`.

# Commands
- Add `#exptoggle [Toggle] - Toggle your or your target's experience gain.`.

# Notes
- Allows operators to turn on/off a player's experience gain individually without changing their rule values.
- The command allows operators to give players access to the command to disable their own experience gain.

utils/sql/git/required/2022_12_15_character_exp_toggle.sql

@@ -0,0 +1,2 @@
+ALTER TABLE `character_data`
+ADD COLUMN `exp_enabled` tinyint(1) UNSIGNED NOT NULL DEFAULT 1 AFTER `exp`;