Consolidate remapper logic into BaseRemapper and update transformers

[HowardZHY]

Motivation

• Reduce duplicated remapper logic by merging common mapping, caching and superclass-merging behavior into a single base class so both legacy and custom remappers share the same implementation.
• Make it easier to maintain class/method/field mapping behavior and parent resolution across the two existing remapper implementations.
• Preserve Forge-specific parent resolution and class-patching behavior while centralizing the generic mapping mechanics.

Description

• Add BaseRemapper which centralizes map/unmap, raw/merged mapping caches, getFieldMap/getMethodMap, and mergeSuperMaps logic (new file: src/main/java/space/libs/asm/BaseRemapper.java).
• Update RemapTransformer to extend BaseRemapper, to populate rawFieldMaps/rawMethodMaps from the parsed ImmutableTable and to use the shared parent-resolution and merging implementation (src/main/java/space/libs/asm/RemapTransformer.java).
• Update CustomRemapRemapper to extend BaseRemapper, call finalizeMappings(...) when loading mappings, and implement getParentInfo(...) using Forge's ClassPatchManager to retain Forge-specific parent/interface resolution (src/main/java/space/libs/asm/CustomRemapRemapper.java).
• Preserve existing special-case behavior such as static-field type lookup and Forge mapping helpers (getRealName/getLegacyName) while removing duplicate mapping code.

Testing

• No automated tests were executed as part of this change.
• Changes were applied and committed locally (Refactor remapper base) but no build or test tasks (e.g. gradle build or unit tests) were run in this rollout.

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Codex Task