[TableGen] Escape single quotes when emitting a string table as char literals (#221612)
Fix a latent bug in StringToOffsetTable, which led to breakage after
#218845
```
C:\_work\llvm-project\llvm-project\build\tools\clang\include\clang/Options/Options.inc(135,18): error: expected expression
C:\_work\llvm-project\llvm-project\build\tools\clang\include\clang/Options/Options.inc(135,24): warning: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
135 | 'D', 'o', 'n', ''', 't', ' ', 'e', 'm', 'i', 't', ' ', 'e', 'r', 'r', 'o', 'r', 's', ' ', 'o', 'n', ' ', 'i', 'n', 'v', 'a', 'l', 'i', 'd', ' ', 'a', 'n', 'a', 'l', 'y', 'z', 'e', 'r', '-', 'c', 'o', 'n', 'f', 'i', 'g', ' ', 'i', 'n', 'p', 'u', 't', 's', '\0',
| ^
```