feat: implement SRAM support for ICS55 in tc_usb2_packet_ram and add corresponding test

tests/rtl/ics55_sram_4096x32_stub.sv

@@ -0,0 +1,31 @@
+// Copyright (c) 2026 Yuchi Miao <miaoyuchi@ict.ac.cn>
+// retroSoC is licensed under Mulan PSL v2.
+
+module SRAM_4096X32_M8_BW (
+    input  logic [11:0] A,
+    input  logic [31:0] D,
+    input  logic        CEB,
+    input  logic        CLK,
+    input  logic        GWEB,
+    input  logic [31:0] WEB,
+    input  logic        MARE,
+    input  logic [ 3:0] MAR,
+    output logic [31:0] Q
+);
+  logic [31:0] s_memory[0:4095];
+
+  always_ff @(posedge CLK) begin
+    if (!CEB) begin
+      if (!GWEB) begin
+        for (int bit_index = 0; bit_index < 32; bit_index++) begin
+          if (!WEB[bit_index]) begin
+            s_memory[A][bit_index] <= D[bit_index];
+          end
+        end
+      end else begin
+        Q <= s_memory[A];
+      end
+    end
+  end
+
+endmodule