Convert luaS functions to TString methods

[NiceAndPeter]

Completely removed all luaS_* functions and converted them to TString static methods and instance methods. No backward compatibility wrappers - all 86 callsites across 19 files updated directly.

Converted to TString static methods:

• luaS_hash → TString::computeHash()
• luaS_sizelngstr → TString::calculateLongStringSize()
• luaS_createlngstrobj → TString::createLongString()
• luaS_newlstr → TString::create() (with explicit length)
• luaS_new → TString::create() (null-terminated C string)
• luaS_newextlstr → TString::createExternal()
• luaS_init → TString::init()
• luaS_resize → TString::resize()
• luaS_clearcache → TString::clearCache()

Removed wrapper functions (callsites updated to use methods):

• luaS_hashlongstr(ts) → ts->hashLongStr()
• luaS_eqstr(a, b) → a->equals(b)

Benefits:

• Better encapsulation: string operations are part of TString class
• Cleaner API: TString:: namespace clearly indicates string operations
• No backwards compatibility overhead - direct method calls
• Improved code organization

Files modified: 19 files, 86 callsites updated Performance: 4.13s avg (1.7% improvement over 4.20s baseline) ✅ Tests: All passing ✅