feat(ingest): add strict_env_syntax mode to config loader

[hsheth2]

Also refactors things into a EnvResolver class.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub

[codecov]

Codecov Report

Attention: Patch coverage is 84.48276% with 9 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...data-ingestion/src/datahub/secret/secret_common.py	0.00%	5 Missing ⚠️
...gestion/src/datahub/configuration/config_loader.py	92.45%	4 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (436b74c) and HEAD (3aa4222). Click for more details.

HEAD has 4 uploads less than BASE

Flag	BASE (436b74c)	HEAD (3aa4222)
ingestion	4	1
ingestion-prefect-plugin	4	3

Files with missing lines	Coverage Δ
...gestion/src/datahub/configuration/config_loader.py	89.83% <92.45%> (-3.57%)	⬇️
...data-ingestion/src/datahub/secret/secret_common.py	0.00% <0.00%> (ø)

... and 204 files with indirect coverage changes

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[codecov]

Codecov Report

Attention: Patch coverage is 86.20690% with 8 lines in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...data-ingestion/src/datahub/secret/secret_common.py	0.00%	5 Missing ⚠️
...gestion/src/datahub/configuration/config_loader.py	94.33%	3 Missing ⚠️

Files with missing lines	Coverage Δ
...gestion/src/datahub/configuration/config_loader.py	93.22% <94.33%> (-0.18%)	⬇️
...data-ingestion/src/datahub/secret/secret_common.py	0.00% <0.00%> (ø)

... and 35 files with indirect coverage changes

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 436b74c...3aa4222. Read the comment docs.