fix: stack block with unrecognized blocks

[i4ki]

Reason for This Change

The parser was not failing for configurations containing a stack block with unrecognized child blocks.

Description of Changes

Makes the parser returns errors for each unrecognized block.

[i4ki]

@katcipis
I got this while testing the extension, it's actually a bug in main but let's merge after the #357 PR is merged so we have this in the changelog of fixes.

[codecov]

Codecov Report

Merging #358 (e1d6391) into main (07c9a37) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #358      +/-   ##
==========================================
+ Coverage   68.02%   68.04%   +0.01%     
==========================================
  Files          37       37              
  Lines        6947     6953       +6     
==========================================
+ Hits         4726     4731       +5     
- Misses       1967     1968       +1     
  Partials      254      254              

Flag	Coverage Δ
tests	68.04% <100.00%> (+0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
hcl/hcl.go	87.55% <100.00%> (+0.08%)	⬆️
manager.go	62.86% <0.00%> (-0.25%)	⬇️

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