Issue #980: Replace AntBuilder.copy() with Files.walkFileTree()

[vivek-0509]

Issue #980:

Description

Replaces the AntBuilder.copy() implementation in copyDir with Java NIO's Files.walkFileTree() and SimpleFileVisitor. This addresses the issues that caused PR #982 to be reverted.

Changes

• Replaced AntBuilder.copy(todir: destination) { fileset(dir: source) } with Files.walkFileTree() and SimpleFileVisitor
• Added proper infinite recursion prevention by:
  1. Skipping directories that are inside the destination
  2. Skipping directories/files whose target would end up inside the source (prevents nested copies when destination is inside source)

Note on Symlinks

The implementation does not follow directory symlinks by default. This is intentional:

• All symlinks in tested repos point to directories already within the same repository
• Not following them avoids copying the same files twice

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Closes #980

[romani]

lets try in real execution

[romani]

triggered at checkstyle/checkstyle#17575 (comment)

[romani]

triggered at checkstyle/checkstyle#18312 (comment)

[romani]

update works fine !!!

@vivek-0509 , thanks a lot.