[breaking] fix: remove tree config lookup

[Bikappa]

Please check if the PR fulfills these requirements

See how to contribute

• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• The PR follows
  our contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)
• configuration.schema.json updated if new parameters are added.

What kind of change does this PR introduce?

Dismiss the automatic config file lookup in the current working directory and its parents.

What is the current behavior?

When the user does not specify a configuration file, the presence of one is checked in the current working directory and iteratively from the closest parent directory to the root.

What is the new behavior?

The described config file lookup is dropped. It becomes possible to specify a configuration file only by the command line flag --config-file or by changing the arduino data directory.

Does this PR introduce a breaking change, and is titled accordingly?

Yes, applications relying on the previous silent current working directory and parents lookup will be disregarded.

Other information

Fixes #758

[codecov]

Codecov Report

Base: 36.56% // Head: 36.52% // Decreases project coverage by -0.04% ⚠️

Coverage data is based on head (bf6da0a) compared to base (c95f890).
Patch coverage: 50.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2085      +/-   ##
==========================================
- Coverage   36.56%   36.52%   -0.04%     
==========================================
  Files         229      229              
  Lines       19538    19526      -12     
==========================================
- Hits         7144     7132      -12     
- Misses      11555    11556       +1     
+ Partials      839      838       -1     

Flag	Coverage Δ
unit	36.52% <50.00%> (-0.04%)	⬇️

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

Impacted Files	Coverage Δ
main.go	0.00% <0.00%> (ø)
configuration/configuration.go	46.34% <100.00%> (-3.66%)	⬇️
arduino/cores/packagemanager/package_manager.go	67.46% <0.00%> (-0.73%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[matthijskooijman]

Shouldn't this be marked as breaking compatibility? And set to close #758?

[Bikappa]

Shouldn't this be marked as breaking compatibility? And set to close #758?

@matthijskooijman yes, that's correct. It will be marked as such once it leaves the draft mode, at the latest.