Replace pkg-up by an inlined solution

[Kocal]

pkg-up is deprecated, and has been replaced by package-up. This one is more lightweight, but is only available as ESM format, which is not compatible with Encore.

So, I've dropped pkg-up and inlined package-up and its single dependency find-up-simple, with some tests.

Removing pkg-up remove a lot of sub-dependencies aswell, which is better in term of security, but also in term of bandwidth and size on disk.

Here, you can see the impact without pkg-up and with package-up, we reduce the bandwidth consumption by ~500 GB (but note that our inlined solution is smaller than package-up):

Package size report
===================

Package info for "@symfony/webpack-encore@4.6.1": 61 MB
  Released: 2024-01-25 17:18:00.95 +0000 UTC (30w1d ago)
  Downloads last week: 48,107 (32.02%)
  Estimated traffic last week: 2.9 TB
  Subdependencies: 634

Removed dependencies:
  - pkg-up@3.1.0: 36 kB (0.05%)
    Downloads last week: 6,317,196 (N/A% from 3.1.0)
    Downloads last week from "@symfony/webpack-encore@4.6.1": 48,107 (N/A%)
    Traffic last week: N/A
    Traffic from "@symfony/webpack-encore@4.6.1": 2.9 TB (N/A%)
    Subdependencies: 6 (0.94%)

Added dependencies:
  + package-up@5.0.0: 13 kB (0.02%)
    Downloads last week: 31,071 (N/A% from 5.0.0)
    Estimated traffic last week: N/A
    Subdependencies: 1 (0.15%)

Estimated new statistics:
  Package size: 61 MB → 51 MB (83.07%)
  Subdependencies: 634 → 486 (-148)
  Traffic with last week's downloads:
    For current version: 2.9 TB → 2.4 TB (498 GB saved)
    For all versions: 9.2 TB → 7.6 TB (1.6 TB saved)