Setting text encoding to fix the newline char issue when using StreamReader

[surgupta-msft]

Issue describing the changes in this PR

resolves #1935

We noticed that the test - BlobTrigger_Stream_Succeeds() shows flaky behavior with one of the following outputs -

1. Test works successfully.
2. Different actual and expected output when the new line is missing -
   • Expected: Hello World
   • Actual: Hello World[2023-09-13T20:36:29.524Z] Executed 'Func···
   • Test run: link
3. Error: Condition not reached within timeout
   • Test run: link

Regarding behavior (3), not seeing this happening recently with many runs I tried via pipeline and not able to repro locally as well, as locally the test always passes.

This PR fixes behavior (2) above, as StreamReader has issues reading newline character and setting the text encoding helps resolving the issue. Ran this PR changes a number of times and did not notice any flaky behavior - runs.

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

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