Fix Maven Sha256 Checksum Issue

[idiskyle]

Description

Changes applied to maven related signing:

• Windows sha256 file encoded by utf8(no BOM)
• powershell script task used latest version, previous 5.1 version only supports utf8 with BOM.
• Windows sha256 file content in format 'sha256value *filename.extension'.
• Linux sha256 file content in format 'sha256value *filename.extension'.

More information about powershell encoding:
Windows powershell encoding reference: about_Character_Encoding - PowerShell | Microsoft Learn

• for version 5.1, it only has 'UTF8 Uses UTF-8 (with BOM).'
• for version v7.1 and higher, it has:
  utf8: Encodes in UTF-8 format (no BOM).
  utf8BOM: Encodes in UTF-8 format with Byte Order Mark (BOM)
  utf8NoBOM: Encodes in UTF-8 format without Byte Order Mark (BOM)

Motivation and Context