Cleanup implants lib and refactor dependencies

[hulto]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

• Renames implants/pkg to implants/lib
• Moves implants/eldritch to implants/lib/eldritch
• Updates relevant paths (e.g. in docs and code)
• Consolidate cargo files in the workspace root

Replaces: #200

Which issue(s) this PR fixes:

[codecov]

Codecov Report

Merging #215 (81311b8) into main (10683d4) will decrease coverage by 0.05%.
The diff coverage is 78.78%.

@@            Coverage Diff             @@
##             main     #215      +/-   ##
==========================================
- Coverage   72.35%   72.30%   -0.05%     
==========================================
  Files          82       82              
  Lines        4666     4676      +10     
==========================================
+ Hits         3376     3381       +5     
- Misses       1205     1210       +5     
  Partials       85       85              

Impacted Files	Coverage Δ
implants/lib/eldritch/src/assets.rs	51.61% <ø> (ø)
implants/lib/eldritch/src/assets/copy_impl.rs	91.30% <ø> (ø)
implants/lib/eldritch/src/assets/list_impl.rs	100.00% <ø> (ø)
implants/lib/eldritch/src/file.rs	66.33% <ø> (ø)
implants/lib/eldritch/src/file/append_impl.rs	100.00% <ø> (ø)
implants/lib/eldritch/src/file/compress_impl.rs	88.00% <ø> (ø)
implants/lib/eldritch/src/file/copy_impl.rs	100.00% <ø> (ø)
implants/lib/eldritch/src/file/download_impl.rs	98.03% <ø> (ø)
implants/lib/eldritch/src/file/exists_impl.rs	100.00% <ø> (ø)
implants/lib/eldritch/src/file/hash_impl.rs	100.00% <ø> (ø)
... and 36 more

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[Cictrone]

if it passed it merges