[MOB-4781] userdefaults migration refactor

[roninopf]

🔹 Jira Ticket(s)

• MOB-4781

✏️ Description

• creates a new migration function in LocalStorage for lastPushPayload
• cleans up/fixes the logic of the auth data migration a little bit for unexpected edge cases

[codecov[bot]]

Codecov Report

Merging #575 (0678d8e) into jay/MOB-4786-separate-mocks (158f8c6) will decrease coverage by 0.03%. The diff coverage is 60.00%.

@@                       Coverage Diff                       @@
##           jay/MOB-4786-separate-mocks     #575      +/-   ##
===============================================================
- Coverage                        85.38%   85.35%   -0.04%     
===============================================================
  Files                               91       91              
  Lines                             6282     6288       +6     
===============================================================
+ Hits                              5364     5367       +3     
- Misses                             918      921       +3     

Impacted Files	Coverage Δ
swift-sdk/Internal/LocalStorage.swift	83.58% <52.94%> (-3.72%)	:arrow_down:
swift-sdk/Internal/IterableUserDefaults.swift	67.59% <100.00%> (+0.61%)	:arrow_up:

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