This PR fixes a bug where values for fields specified in the truncateHl7Fields setting were being completely removed instead of being truncated.

Test Steps:

add fields to a receiver's truncateHl7Fields setting. For example:

translation: !<HL7>
    schemaName: "classpath:/metadata/hl7_mapping/ORU_R01/ORU_R01-base.yml"
    truncateHl7Fields: "ORC-12-3, OBR-16-3, ORC-12-1, OBX-15-2"

Note each field's maximum length. Use https://hl7-definition.caristix.com/v2/HL7v2.5/Segments as a reference.
Use a sample fhir bundle and replace values for the fields that were specified in the truncateHl7Fields setting with strings that are the size of each field's maximum length. Add "TRUNCATE THIS" at the end of each string.
Use http://localhost:7071/api/reports to send a report to the receiver
Verify that the HL7 file that was created contains the original values for the fields without the "TRUNCATE THIS" strings.

Changes

bug fix: remove index from path before sending to terser
added tests for truncation with different ways that an hl7FieldPath can be formed

Checklist

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?