chore(build): fix nightly repeated unit tests

[thisisabhash]

Issue #

Nightly unit tests are failing due to timeout and flaky tests.
https://github.com/aws-amplify/amplify-swift/actions/workflows/nightly_repeated_unittest.yml

Description

This PR

• increases the the timeout for the workflow from 50 min to 120 mins.
• reduces the number of iterations to 5 ensure the test completes within the time limit.
• runs each test without building
• disables retry for each scheme
• disables parallel testing
• identifies flaky tests and skips them

The flaky tests will be resolved in follow up PRs.

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.76%. Comparing base (1e24d45) to head (5a03c70).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #4048       +/-   ##
===========================================
- Coverage   78.61%   67.76%   -10.85%     
===========================================
  Files         211     1129      +918     
  Lines       14188    52482    +38294     
===========================================
+ Hits        11154    35566    +24412     
- Misses       3034    16916    +13882     

Flag	Coverage Δ
API_plugin_unit_test	70.33% <ø> (?)
AWSPluginsCore	69.25% <ø> (ø)
Amplify	47.93% <ø> (?)
Analytics_plugin_unit_test	85.20% <ø> (ø)
Auth_plugin_unit_test	73.57% <ø> (?)
DataStore_plugin_unit_test	83.30% <ø> (-0.13%)	⬇️
Geo_plugin_unit_test	74.86% <ø> (ø)
Logging_plugin_unit_test	65.27% <ø> (ø)
Predictions_plugin_unit_test	34.77% <ø> (?)
PushNotifications_plugin_unit_test	88.43% <ø> (?)
Storage_plugin_unit_test	79.39% <ø> (?)
unit_tests	67.76% <ø> (-10.85%)	⬇️

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