Add support for 1.21.1

[Gilly7CE]

This PR introduces a support change for Minecraft (MC) 1.21.1. This directly bumps main from 1.20.4 to 1.21.1 so it includes fixes to 1.20.5 & 1.20.6 breaking changes. A PR to update the 1.20.x branch to 1.20.6 will be done separately.

Full list of changes:

• Update Gradle to 8.10 and Loom to 1.7-Snapshot
• Update MC support to 1.21.1
• Fix breaking change to BlockBreakingSpeedRatioCalculator following enchantment code changes in MC
• Replace EndFrameBlock_EyeToggleMixin with EnderEyeItem_EyeToggleMixin following removal of deprecated methods in Block code
• Fix mixin definitions following MC code changes
• Replace mixins for flower pots with single mixin and introduce functional approach to dealing with which rule to implement
• Replace PlayerEntity_PortalSpectactorDelayMixin with NetherPortalBlock_PortalBlockMixin following portal interaction changes
• Refactor spectator portal rule code to not use networking sync between server and client but two mixins for server and client which executes the same logic, like in vanilla. Networking changes in 1.20.5 caused a breaking change here and it would be too complicated to keep around for a single use case. The new implementation is likely more future proof.

[Gilly7CE]

Keeping in draft until pipeline issue is fixed and I've tested all rules affected by breaking changes

[Gilly7CE]

Keeping in draft until pipeline issue is fixed and I've tested all rules affected by breaking changes

Fixed one issue to do with instant mining where the game crashed

Two rules to fix:

• [x] replaceFlowerInPot
• [x] alwaysPickFlowersFromPot
• [x] dropAllXpOnDeath

[Gilly7CE]

Keeping in draft until pipeline issue is fixed and I've tested all rules affected by breaking changes

Fixed one issue to do with instant mining where the game crashed

Two rules to fix:

• [x] replaceFlowerInPot
• [x] alwaysPickFlowersFromPot
• [x] dropAllXpOnDeath

These rules have now been fixed. Introduced a single mixin for the flower pot rules to manage the order instead of using mixin shifts. This will be more stable.