[DebugInfo] Error if unsupported address size detected in line table

Prior to this patch, if a DW_LNE_set_address opcode was parsed with an
address size (i.e. with a length after the opcode) of anything other 1,
2, 4, or 8, an llvm_unreachable would be hit, as the data extractor does
not support other values. This patch introduces a new error check that
verifies the address size is one of the supported sizes, in common with
other places within the DWARF parsing.

This patch also fixes calculation of a generated line table's size in
unit tests. One of the tests in this patch highlighted a bug introduced
in 1271cde4, when non-byte operands were used as arguments for
extended or standard opcodes.

Reviewed by: dblaikie

Differential Revision: https://reviews.llvm.org/D73962