Support for fetching FHIR resources via Bulk export mode

[chandrashekar-s]

Description of what I changed

Fixes #1031

• Changes to support fetching of FHIR resources from FHIR server via Bulk Export API. Currently, changes are made only for FULL_RUN, INCREMENTAL_RUN changes will be made in a separate PR.
• A parameter called fhirFetchMode has been added, which explicitly specifies which mode the application should use to fetch FHIR resources from source (this avoids the confusion of dynamically figuring out the mode from the parameters configured).

E2E test

• Added a e2e test for BULK_EXPORT mode.
• Added unit tests.

TESTED:

• Manually tested the application by triggering a FULL run from the controller UI.

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

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 37.25490% with 192 lines in your changes missing coverage. Please review.

Project coverage is 51.63%. Comparing base (1db3398) to head (30b4fe9).

Files	Patch %	Lines
...c/main/java/com/google/fhir/analytics/FhirEtl.java	0.00%	58 Missing :warning:
...java/com/google/fhir/analytics/BulkExportUtil.java	45.36%	43 Missing and 10 partials :warning:
...main/java/com/google/fhir/analytics/FetchUtil.java	5.40%	35 Missing :warning:
...ava/com/google/fhir/analytics/PipelineManager.java	37.50%	15 Missing :warning:
...java/com/google/fhir/analytics/FhirSearchUtil.java	72.09%	5 Missing and 7 partials :warning:
...java/com/google/fhir/analytics/DataProperties.java	20.00%	6 Missing and 2 partials :warning:
...e/fhir/analytics/converter/JsonDateSerializer.java	0.00%	4 Missing :warning:
...e/fhir/analytics/model/BulkExportHttpResponse.java	57.14%	3 Missing :warning:
...oogle/fhir/analytics/model/BulkExportResponse.java	81.81%	0 Missing and 2 partials :warning:
...fhir/analytics/converter/JsonDateDeserializer.java	60.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1082 +/- ## ============================================ - Coverage 51.92% 51.63% -0.30% - Complexity 697 725 +28 ============================================ Files 91 98 +7 Lines 5519 5746 +227 Branches 709 732 +23 ============================================ + Hits 2866 2967 +101 - Misses 2390 2497 +107 - Partials 263 282 +19 ```

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[chandrashekar-s]

Hi @bashir2, this PR contains changes to support FULL_RUN only. I will raise a separate PR for supporting INCREMENTAL_RUN (have created this issue for the same).