Add options to customize UserFeedback error messages

[itaybre]

Adds customization to error messages in user feedback.

Closes: #4720

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Generated by 🚫 dangerJS against 90a23f9

[github-actions]

• 🚫 The changelog entry seems to be part of an already released section ## 9.0.0.
  Consider moving the entry to the ## Unreleased section, please.

[codecov]

Codecov Report

❌ Patch coverage is 37.50000% with 5 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@d5360f3). Learn more about missing BASE report.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...UserFeedback/SentryUserFeedbackFormViewModel.swift	0.000%	3 Missing ⚠️
...serFeedback/SentryUserFeedbackFormController.swift	0.000%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main     #6790   +/-   ##
========================================
  Coverage        ?   84.486%           
========================================
  Files           ?       448           
  Lines           ?     27298           
  Branches        ?     11954           
========================================
  Hits            ?     23063           
  Misses          ?      4188           
  Partials        ?        47           

Files with missing lines	Coverage Δ
...guration/SentryUserFeedbackFormConfiguration.swift	100.000% <100.000%> (ø)
...serFeedback/SentryUserFeedbackFormController.swift	26.229% <0.000%> (ø)
...UserFeedback/SentryUserFeedbackFormViewModel.swift	84.384% <0.000%> (ø)

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