Added support to read FHIR resources from NDJson file

[chandrashekar-s]

Description of what I changed

Fixes #362 Added support for reading FHIR resources from NDJson file.

E2E test

Added unit tests

TESTED:

Tested end-to-end by running the pipeline for ndjson files using the following command and verifed if the parquet files are created correctly.

    com.google.fhir.analytics.FhirEtl \
    --outputParquetPath=/tmp/TEST/ \
    --sourceNDJsonFilePattern=/tmp/ndjson/* \
    --resourceList=Patient,Encounter,Observation

Checklist: I completed these to help reviewers :)

• [x] I have read and will follow the review process.

• [x] I am familiar with Google Style Guides for the language I have coded in.

  No? Please take some time and review Java and Python style guides.

• [x] My IDE is configured to follow the Google code styles.

  No? Unsure? -> configure your IDE.

• [x] I have added tests to cover my changes. (If you refactored existing code that was well tested you do not have to add tests)

• [x] I ran mvn clean package right before creating this pull request and added all formatting changes to my commit.

• [x] All new and existing tests passed.

• [x] My pull request is based on the latest changes of the master branch.

  No? Unsure? -> execute command git pull --rebase upstream master

[chandrashekar-s]

Thanks @bashir2 for the review, I have addressed the review comments in the latest commit. Please have a look.