nanobsd: Use local repository cache for precompiled package base builds

[senguptaangshuman17_gmail.com]

Summary

Fetch pkgbase packages into a local repository (FreeBSD-local) before installing. Rewrite _xxx_pkg_metalog() to deduplicate METALOG entries and split target database regeneration into _xxx_run_pkg_scripts().

Add metalog_add_data() to append metalog lines with sensible mode defaults.

[senguptaangshuman17_gmail.com]

Rename revision, normalize XXXJL comments, restore normalized fingerprints comment

[senguptaangshuman17_gmail.com]

Rebase stack on top of D59043 update

[jlduran]

tools/tools/nanobsd/defaults.sh

304

This change should be done in D58950.

370

This change should be done in D58952.

490

This comment change is not related to this commit, I believe it should be done in D58951.

522

This comment change is not related to this commit, I believe it should be done in D58954.

594

This change should be done in D58951.

881–895

This (location) change should be done in D58931. It is a non-functional change (NFC) that just changes the location of the function to keep it together (alphabetically?) with other tgt_ functions.

[senguptaangshuman17_gmail.com]

Clean up pkgbase world list logic and remove duplicate sed fixups