[eas-cli] Refactor getExpoConfig to remove dangerous default

[wschurman]

Why

We had a bug where we were accidentally putting the private config in the public config due to a tough-to-catch refactoring error. This PR is an effort to make refactoring errors like this less likely in the future.

expo/sentry-expo#321 (comment)

Closes ENG-7940.

How

Separate out private and public config getters to make it clearer that there is a difference in name and type from the private and public expo configs. This should help code reviewers catch errors during refactors.

Test Plan

Run all tests.

[linear]

ENG-7940 Refactor getProjectConfig

https://exponent-internal.slack.com/archives/C013ZK4SA12/p1678919589205769?thread_ts=1678876491.332049&cid=C013ZK4SA12

[wschurman]

/changelog-entry chore Refactor getExpoConfig to remove dangerous default

[github-actions]

Size Change: -354 B (0%)

Total Size: 41.5 MB

Filename	Size	Change
./packages/eas-cli/dist/eas-linux-x64.tar.gz	41.5 MB	-354 B (0%)

_{compressed-size-action}

[codecov]

Codecov Report

Merging #1857 (3c0fd3a) into main (e302390) will decrease coverage by 0.00%.
The diff coverage is 57.15%.

@@            Coverage Diff             @@
##             main    #1857      +/-   ##
==========================================
- Coverage   52.75%   52.74%   -0.00%     
==========================================
  Files         474      474              
  Lines       17050    17064      +14     
  Branches     3405     3410       +5     
==========================================
+ Hits         8993     8999       +6     
- Misses       8040     8048       +8     
  Partials       17       17              

Impacted Files	Coverage Δ
packages/eas-cli/src/build/createContext.ts	24.08% <0.00%> (ø)
packages/eas-cli/src/build/runBuildAndSubmit.ts	24.52% <0.00%> (ø)
packages/eas-cli/src/commands/branch/create.ts	45.17% <ø> (ø)
packages/eas-cli/src/commands/branch/delete.ts	30.19% <ø> (ø)
packages/eas-cli/src/commands/branch/list.ts	56.25% <ø> (ø)
packages/eas-cli/src/commands/branch/rename.ts	35.00% <ø> (ø)
packages/eas-cli/src/commands/branch/view.ts	45.84% <ø> (ø)
packages/eas-cli/src/commands/build/cancel.ts	51.32% <ø> (ø)
packages/eas-cli/src/commands/build/configure.ts	40.91% <ø> (ø)
packages/eas-cli/src/commands/build/index.ts	20.54% <ø> (ø)
... and 52 more

[github-actions]

✅ Thank you for adding the changelog entry!