feat(csharp) .NET 8.0 code migration (#966)

* .net 8.0 migration

* update docs

* revert change

* revert change and update appendix docs

* remove static

* Update binary_search_insertion.cs

* Update binary_search_insertion.cs

* Update binary_search_edge.cs

* Update binary_search_insertion.cs

* Update binary_search_edge.cs

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/csharp/chapter_searching/linear_search.cs

@@ -8,7 +8,7 @@ namespace hello_algo.chapter_searching;
 
 public class linear_search {
     /* 线性查找（数组） */
-    static int LinearSearchArray(int[] nums, int target) {
+    int LinearSearchArray(int[] nums, int target) {
         // 遍历数组
         for (int i = 0; i < nums.Length; i++) {
             // 找到目标元素，返回其索引
@@ -20,7 +20,7 @@ public class linear_search {
     }
 
     /* 线性查找（链表） */
-    static ListNode? LinearSearchLinkedList(ListNode? head, int target) {
+    ListNode? LinearSearchLinkedList(ListNode? head, int target) {
         // 遍历链表
         while (head != null) {
             // 找到目标节点，返回之
@@ -37,7 +37,7 @@ public class linear_search {
         int target = 3;
 
         /* 在数组中执行线性查找 */
-        int[] nums = { 1, 5, 3, 2, 4, 7, 5, 9, 10, 8 };
+        int[] nums = [1, 5, 3, 2, 4, 7, 5, 9, 10, 8];
         int index = LinearSearchArray(nums, target);
         Console.WriteLine("目标元素 3 的索引 = " + index);