fix(yaml): bubble up rules struct unmarshal errors

[ecrupper]

It looks like these two unchecked unmarshal calls were part of the initial go-vela/types commit, so I am not sure if there is some extra backstory here that I'm missing. However, it would be nice to bubble up errors here, since suppressing them just returns an empty rules block which gets converted to no rules.

ruleset:
  branch:
  event: push
  branch: main

converts to -->

Before:

ruleset:
  operator: and
  matcher: filepath

After:

error: "mapping key \"branch\" already defined"

FWIW, the unmarshaler is not strict on fields, so this won't break pipelines that are using unknown fields (threw in a test just to confirm).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.60%. Comparing base (1e93bf1) to head (9260f1e).
Report is 1 commits behind head on main.

❌ Your project status has failed because the head coverage (56.60%) is below the target coverage (90.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1256   +/-   ##
=======================================
  Coverage   56.60%   56.60%           
=======================================
  Files         629      629           
  Lines       35653    35654    +1     
=======================================
+ Hits        20180    20181    +1     
  Misses      14792    14792           
  Partials      681      681           

Files with missing lines	Coverage Δ
compiler/types/yaml/yaml/ruleset.go	63.18% <100.00%> (+0.18%)	⬆️