Update FHIRFunctions to base64 encode messages going to poison queue

[arnejduranovic]

This PR updates FHIRFunctions to base64 encode poison queue messages in order to fix #16609.

Test Steps:

1. Follow repro steps in ticket but now see that the poison queue message does actually trigger the translate step to run

Changes

• FHIRFunctions now base64 encoded messages being put in the poison queue
• Tests updated to expect base64 encoded messages

Testing

• [x] Tested locally?
• [x] Ran ./prime test or ./gradlew testSmoke against local Docker ReportStream container?
• [ ] (For Changes to /frontend-react/...) Ran npm run lint:write?
• [x] Added tests?

Linked Issues

• Fixes #16609

[github-actions[bot]]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

OpenSSF Scorecard

Package	Version	Score	Details

Scanned Manifest Files

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Test Results

1 247 tests  ±0   1 243 :white_check_mark: ±0   7m 44s :stopwatch: +23s   162 suites ±0       4 :zzz: ±0    162 files   ±0       0 :x: ±0 

Results for commit 722d10d6. ± Comparison against base commit 448460ad.

:recycle: This comment has been updated with latest results.

[jalbinson]

My PR isn't currently merged but I added some handy extension functions to simplify encoding calls

https://github.com/CDCgov/prime-reportstream/pull/16495/files#diff-90f91fee9a7b7cdf96f4bb6f1e35055e935d3c4383f98172ac4b1ef6e7764eb1R52-R53

[sonarcloud[bot]]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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Integration Test Results

 54 files   54 suites   28m 19s :stopwatch: 414 tests 404 :white_check_mark: 10 :zzz: 0 :x: 417 runs  407 :white_check_mark: 10 :zzz: 0 :x:

Results for commit 722d10d6.