Symbol map reuse for consistent re-obfuscation (upstream #168)

[mcpolo99]

Upstream: mkaring#168

Support loading a previous symbol map for consistent name mappings across builds.
Action: Implement symbol map import/export.

[mcpolo99]

yck1509#680

[mcpolo99]

Resolved by #96 (squash-merged to develop as 495ee4c). Implemented InputSymbolMap (upstream mkaring#168 / yck1509#680): feed a previous run's symbols.map back in and the renamer reuses those obfuscated names, so re-obfuscation stays consistent across builds. Available via the .crproj inputSymbolMap attribute, the CLI --map flag, and a GUI field in Advanced Settings. Proven by SymbolMapReuse.Test (different seeds → identical maps with the input map; different without it).