Refactor ASF Celix file utils and FILE* usage to work with libuv Stream Abstraction

[pnoltes]

Introduction

Refactor file utilities that currently use FILE* to use libuv's file and stream abstractions (uv_fs_t, uv_file). This ensures better cross-platform file handling.

Steps

• Replace FILE* usage in the public api with uv_file

This includes the celix_filter.h, celix_properties.g, celix_bundle context.h headers and many more.

• Replace FILE* usage in the internal code

This includes usage of fprintf, open_memstream, etc.