Change instance variable numbers for line numbers instead of counter

還沒有人認領這個 Issue。

Whenever we are creating a new instance of a variable or a fresh one, we keep the variable name and concatenate it with an incremental counter (e.g., a0, x1, y2).
A simple change would be to use the line number where this value was introduced, instead of the counter.
Example:

The error could be `#x_25 == #x_24 - 10` where `24` and `25` are the lines where these were introduced.
A question could be, if multiple vars are changed could we still use the same tactic? Lets try and make some tests to see.

首先定位建立新執行個體變數名稱的程式碼，以及針對產生名稱的現有測試。檢查在每個引入位置如何取得行號，然後新增測試，涵蓋提議的以行為基礎的名稱，以及多個變數同時發生變更的情況；完成的標準是測試定義並確認預期的命名行為。

由索引模型根據 Issue 內容生成。