Remove unused variables and functions surrounding the `xxPast` event flags.

`Context::ApplyItemEffect` should be done except for ITEMTYPE_ITEM, which has been started.

…teHelpers.

…l keys part of `ApplyItemEffect` to those functions.

…riable from Logic.

Add Zelda's Letter, Ruto's Letter, and Weird Egg to `HasItem` and `CanUse`.

Change Stone of Agony to HasItem variant.

… and biggoron swords to CanUse, and membership card to HasItem.

…tons to HasItem.

…ved their standalone variables.

…tItem.

…bles. `HasItem(RG_HOOKSHOT)` just checks both hookshot and longshot.

Improve progressive ocarina and progressive hookshot application.
Convert Bottles and NumBottles to inventory slot checks.
Add `bool exact` argument to `CheckInventory` to allow for checking for any item or specific item in each slot.

Convert Slingshot, MagicMeter, BombBag, and Bow helper variables to SCL format.

… savecontext-logic

Get it "generating" after merge. Generation still fails.

Fix multiple ApplyItemEffect bugs.