NDISC: option parsing is the same for all NDISC types

[thvdveld]

This removes the foreach_option function and instead tries to parse all options. Since the way options are parsed is the same for all messages, this is a bit more efficient in terms of code size.

Running cargo bloat --release --example server --filter smoltcp:
On main: 216.3KiB
On this branch: 213.9KiB

Running cargo bloat --release --example sixlowpan --filter smoltcp:
On main: 213.9KiB
On this branch: 211.4KiB

[codecov]

Codecov Report

Attention: 15 lines in your changes are missing coverage. Please review.

Comparison is base (8a86a5a) 79.74% compared to head (2d862b2) 79.76%.

Files	Patch %	Lines
src/wire/ndisc.rs	68.08%	15 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #878      +/-   ##
==========================================
+ Coverage   79.74%   79.76%   +0.01%     
==========================================
  Files          78       78              
  Lines       28131    28092      -39     
==========================================
- Hits        22433    22407      -26     
+ Misses       5698     5685      -13     

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