[security] Alpine version old , leading to Security vulnerabilities

[nitinSophos]

Bug Description

We are using Old Alpine Image 3.12.0 , latest is 3.15.0
Old alpin image has multiple vulnerabilities including Libssl 1.1.1k , and LibreSSL. (This is not an exhaustive list)

Fix: Update alpine base image in both frpc and frps docker image.

frpc Version

0.38.0

frps Version

0.38.0

System Architecture

linux/amd64

Configurations

N/A

Logs

N/A

Steps to reproduce

No response

Affected area

• Docs
• Installation
• Performance and Scalability
• Security
• User Experience
• Test and Release
• Developer Infrastructure
• Client Plugin
• Server Plugin
• Extensions
• Others

[nitinSophos]

Raised PR: #2731