Add support for LF_TAGGED_UNION, LF_TUCASE

[nikitalita]

These appear to have been added quite recently to the format; they're present in the latest DIA SDK that comes with Visual Studio 2022 (17.7.6)

LF_TAGGED_UNION = 0x151e
Appears to have the same structure as LF_UNION2
Has a UdtType of UdtTaggedUnion

LF_TUCASE = 0x1520
Corresponds to SymTagTaggedUnionCase in the latest cvconst.h (Visual Studio 2022, 17.7.6)
Unsure of which symbol record that SymTagTaggedUnionCase corresponds to; they don't appear to have added any additional S_ symbol records that you don't already have.
Appears to have a type index and a name as members.