docs(packages): add epic spec and subissue drafts for packages overhaul #1669

[josecelano]

Related to #1669

Adds the EPIC spec and 10 subissue draft specs for the packages overhaul tracked in issue #1669.

What's included

• docs/issues/open/1669-overhaul-packages/EPIC.md — master EPIC spec with:

  • Package inventory (current state, 26 packages across 3 prefixes)
  • Desired package state tables
  • Active subissues with SI-XX ordering, priority rules (M/U/P/E), and blocker chains
  • Delivery strategy, open questions, extraction ordering analysis

• 10 subissue draft specs (docs/issues/drafts/1669-NN-*.md):

  • SI-02 — Move DurationSinceUnixEpoch from primitives to clock
  • SI-03 — Move DEFAULT_TIMEOUT from configuration to clock
  • SI-04 — Align torrust- prefix (rename 7 packages to torrust-tracker-)
  • SI-05 — Rename torrust-tracker-metrics → torrust-metrics
  • SI-06 — Rename torrust-tracker-clock → torrust-clock
  • SI-07 — Rename torrust-tracker-located-error → torrust-located-error
  • SI-08 — Extract torrust-tracker-contrib-bencode → torrust-bencode
  • SI-09 — Extract torrust-clock to standalone repository
  • SI-10 — Extract torrust-metrics to standalone repository
  • SI-11 — Extract torrust-tracker-client to standalone repository

Draft — work in progress; specs are not yet finalized or reviewed.