Make 'field is not accessible' and 'field initialized twice' errors point to the field inside the obj construction

[ire4ever1190]

Fixes two line infos to make the error's clearer inside editors

• 'field is not accessible' would point to the whole object construction instead of just the field inside the construction
• 'field initialized twice' would point to the colon instead of the field

[github-actions]

Thanks for your hard work on this PR!
The lines below are statistics of the Nim compiler built from 6bc5273

Hint: mm: orc; opt: speed; options: -d:release
178145 lines; 8.632s; 653.828MiB peakmem