feat: support takePicture.

[yujune]

Introduced the takePicture function in MobileScannerController to allow pictures to be captured programmatically.

• Related Issue: takePicture via MobileScannerController #1262

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 38.51%. Comparing base (715c50f) to head (a6217c4).

Files with missing lines	Patch %	Lines
lib/src/mobile_scanner_controller.dart	0.00%	4 Missing ⚠️
.../method_channel/mobile_scanner_method_channel.dart	0.00%	2 Missing ⚠️
lib/src/mobile_scanner_platform_interface.dart	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1479      +/-   ##
===========================================
- Coverage    38.84%   38.51%   -0.33%     
===========================================
  Files           42       42              
  Lines          950      958       +8     
===========================================
  Hits           369      369              
- Misses         581      589       +8     

Flag	Coverage Δ
unittests	38.51% <0.00%> (-0.33%)	⬇️

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