Use http-intake.logs for logs intake

[tianchu]

What does this PR do?

• Use http-intake.logs endpoint for logs intake.
• Deprecate option DdUsePrivateLink because no need to use a special intake endpoints for PrivateLink anymore.
• Fixes PrivateLink URLs are different from the DNS addresses exposed by the VPC Endpoints #505
• Update PrivateLink instructions on README
• Fix a typo that sets a meaningless env var DD_ on the forwarder

Motivation

The lambda-http-intake.logs endpoint has been merged into the http-intake.logs endpoint on Datadog backend. http-intake.logs can be exposed directly over PrivateLink, which simplifies configurations for Forwarders deployed in private VPC subnets.

Testing Guidelines

• Forwarder deployed in a private VPC subnet can still send logs to Datadog.

Additional Notes

The changes are backward-compatible. When upgrading existing installations with DdUsePrivateLink enabled, the parameter will be kept as true and the Forwarder will continue to use the special set of endpoints for intake.

Types of changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)
• This PR passes the unit tests
• This PR passes the installation tests (ask a Datadog member to run the tests)

[DarcyRaynerDD]

Note, that we use the "aws_forwarder" track.

datadog-serverless-functions/aws/logs_monitoring/logs.py

Line 311 in 24dff24

_HEADERS["DD-EVP-ORIGIN"] = "aws_forwarder"