This patch changes the implementation of DW_OP_piece to use
llvm::BitVector instead of the lldb_private::Value.
This allow to have more granularity which would be useful to implement
DW_OP_bit_piece but also when combined with a second BitVector for
masking the unknown bits/bytes, improves the DWARF Expression
evaluation Since it will show a future patch, the unknown bits/bytes as
optimised rather than showing - misleading - zeroes.
Additionally, this patch fixes a overloading resolution on the Scalar
constructor when using fixed-size interger types instead of fundamentale types.
It also fixes a bug when requesting a Scalar size when the value is less
than a byte.
Signed-off-by: Med Ismail Bennani <firstname.lastname@example.org>