Update the minimum deployment target for each platform xcode 27

[SB-shivamgarg]

Changeset

Update minimum deployment targets to iOS 15.0, tvOS 15.0, watchOS 9.0, and macOS 12.0.

Testing

The build is completing without errors and the unit test cases are passing.
The example app is working fine.

[github-actions]

Bugsnag.framework binary size decreased by 22,088 bytes from 940,680 to 918,592 🎉

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [NEW] +22.8Ki  [NEW] +22.8Ki    __DATA_CONST,__cfstring
  [NEW] +16.7Ki  [NEW] +16.7Ki    __TEXT,__objc_methlist
  [NEW] +7.94Ki  +144% +13.5Ki    [__LINKEDIT]
   +17% +4.61Ki   +17% +4.61Ki    [__TEXT]
  [NEW] +3.96Ki  [NEW] +3.96Ki    __DATA_CONST,__const
  [NEW] +2.27Ki  [NEW] +2.27Ki    [__DATA_CONST]
  [NEW] +1.74Ki  [NEW] +1.74Ki    __DATA_CONST,__got
  +8.2%    +728  +8.2%    +728    __DATA,__objc_selrefs
  -0.1%    -389  -0.1%    -429    [22 Others]
  [DEL] -1.31Ki  [DEL] -1.31Ki    Export Info
  [DEL] -1.41Ki  [DEL] -1.41Ki    __DATA,__la_symbol_ptr
  -1.1% -2.06Ki  -1.1% -2.06Ki    Symbol Table
  [DEL] -2.13Ki  [DEL] -2.13Ki    __TEXT,__stub_helper
  [DEL] -2.46Ki  [DEL] -2.46Ki    Rebase Info
  -1.1% -2.86Ki  -1.1% -2.86Ki    __TEXT,__text
  [DEL] -3.14Ki  [DEL] -3.14Ki    Binding Info
 -22.0% -3.53Ki -55.6% -3.49Ki    [__DATA]
  [DEL] -3.96Ki  [DEL] -3.96Ki    __DATA,__const
  [DEL] -4.36Ki  [DEL] -4.36Ki    Lazy Binding Info
  [DEL] -22.8Ki  [DEL] -22.8Ki    __DATA,__cfstring
 -50.1% -31.9Ki -50.1% -31.9Ki    __DATA,__objc_const
  -2.3% -21.6Ki  -1.7% -16.0Ki    TOTAL

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