[WIP][MooreToCore] Fix conversion to vector of bit

$ ./bin/circt-verilog /tmp/string_bit_array.sv
module {
  hw.module @top() {
    %0 = llhd.constant_time <0ns, 0d, 1e>
    %c0_i80 = hw.constant 0 : i80
    %c6_i4 = hw.constant 6 : i4
    %c0_i112 = hw.constant 0 : i112
    %a = llhd.sig %c0_i112 : i112
    llhd.process {
      %1 = builtin.unrealized_conversion_cast %c6_i4 : i4 to i32
      %2 = comb.concat %c0_i80, %1 : i80, i32
      llhd.drv %a, %2 after %0 : !hw.inout<i112>
      llhd.halt
    }
    hw.output
  }
}

lib/Conversion/MooreToCore/MooreToCore.cpp

@@ -558,23 +558,19 @@ struct ConstantOpConv : public OpConversionPattern<ConstantOp> {
 struct StringConstantOpConv : public OpConversionPattern<StringConstantOp> {
   using OpConversionPattern::OpConversionPattern;
   LogicalResult
-  matchAndRewrite(StringConstantOp op, OpAdaptor adaptor,
+  matchAndRewrite(moore::StringConstantOp op, OpAdaptor adaptor,
                   ConversionPatternRewriter &rewriter) const override {
-        // Retrieve the string constant from the op
-    StringRef stringValue = op.getValue();
-
-    // Define the target bit width and radix
-    unsigned radix = 10; // For decimal interpretation; change to 16 for hex, etc.
-
-    // Parse the string as an integer using StringRef::getAsInteger
-    APInt value;
-    stringValue.getAsInteger(radix, value);
-    auto type = rewriter.getIntegerType(value.getBitWidth());
-
-    /* rewriter.replaceOpWithNewOp<hw::ConstantOp>(op, type, value); */
-    rewriter.replaceOpWithNewOp<hw::ConstantOp>(
-        op, type, rewriter.getIntegerAttr(type, value));
-
+    StringRef str = op.getValue();
+    const auto byteSize = sizeof(uint8_t);
+    const unsigned byteWidth = str.size() * byteSize;
+    APInt value(byteWidth, 0);
+    for (size_t i = 0; i < str.size(); ++i) {
+      uint8_t asciiChar = static_cast<uint8_t>(str[i]);
+      value |= APInt(byteWidth, asciiChar) << (byteSize * (str.size() - 1 - i));
+    }
+    auto type = IntegerType::get(rewriter.getContext(), byteWidth);
+    rewriter.replaceOpWithNewOp<hw::ConstantOp>( op, type,
+        rewriter.getIntegerAttr(type, value));
     return success();
   }
 };