Go: Add ability to run all file or package tests

[lzakharov]

Problem Description:

Currently, Zed provides a button to run individual tests. However, there is no similar feature to run all tests within a file or an entire package. This can be inconvenient for developers who want to quickly verify the state of all tests without running them individually.

Proposed Solution:

I propose adding a feature that allows users to run all tests in a file or an entire package with a single action. This could be implemented as a button, similar to the existing function for running individual tests. The button can be located next to the line where the package name is declared, offering intuitive access for users who wish to run all tests in that file or package.

Example