Improve routing capabilities (LP: #1892272) (LP: #1805038)

[slyon]

Description

• Supporting additional route types: anycast, broadcast, local, multicast, nat, throw, xresolve (supported by systemd-networkd as of v243)
• Not assuming a type: unicast, scope: global, by default, but making the default scope depend on the route type:
  • local -> host
  • nat -> host
  • broadcast -> link
  • multicast -> link
  • anycast -> link
  • unicast without gateway/via -> link
  • unicast with gateway/via -> global
  • global otherwise

This only affects the systemd-networkd backend renderer as for NetworkManager only "unicast" routes are supported.

FR-1798
FR-1078
FR-1077

Checklist

• Runs make check successfully.
• Retains 100% code coverage (make check-coverage).
• New/changed keys in YAML format are documented.
• (Optional) Adds example YAML for new feature.
• (Optional) Closes an open bug in Launchpad. LP#1892272 & LP#1805038

[codecov-commenter]

Codecov Report

Merging #248 (df2a5f2) into main (3e3c371) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #248   +/-   ##
=======================================
  Coverage   99.10%   99.10%           
=======================================
  Files          58       58           
  Lines       10055    10078   +23     
=======================================
+ Hits         9965     9988   +23     
  Misses         90       90           

Impacted Files	Coverage Δ
tests/generator/test_errors.py	100.00% <ø> (ø)
src/parse.c	99.81% <100.00%> (+<0.01%)	⬆️
tests/generator/test_routing.py	100.00% <100.00%> (ø)

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[schopin-pro]

LGTM, merging.

[schopin-pro]

Well, I'll let you rebase and merge is more like it, but still, nice work :)