Fix python packaging and running the snowflake integration on CF

[sarah-witt]

What does this PR do?

• Instructs the agent to infer the correct python home instead of explicitly setting it

Previously, we were manually setting PYTHONHOME which did not fully set the path and thus made the snowflake check fail, which has a dependency that calls the platform.platform() standard library function which looks for the current executable:

2022-11-14 14:43:56 UTC | CORE | DEBUG | (pkg/collector/python/loader.go:150 in Load) | Unable to load python module - datadog_checks.snowflake: unable to import module 'datadog_checks.snowflake': Traceback (most recent call last):
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/site-packages/datadog_checks/snowflake/__init__.py", line 14, in <module>
    from .check import SnowflakeCheck
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/site-packages/datadog_checks/snowflake/check.py", line 6, in <module>
    import snowflake.connector as sf
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/site-packages/snowflake/connector/__init__.py", line 15, in <module>
    from .connection import SnowflakeConnection
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/site-packages/snowflake/connector/connection.py", line 34, in <module>
    from . import errors, proxy
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/site-packages/snowflake/connector/errors.py", line 14, in <module>
    from .description import CLIENT_NAME, SNOWFLAKE_CONNECTOR_VERSION
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/site-packages/snowflake/connector/description.py", line 17, in <module>
    PLATFORM = platform.platform()
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/platform.py", line 1206, in platform
    libcname, libcversion = libc_ver(sys.executable)
  File "/var/vcap/jobs/dd-agent/packages/dd-agent/embedded/lib/python3.8/platform.py", line 193, in libc_ver
    with open(executable, 'rb') as f:
FileNotFoundError: [Errno 2] No such file or directory: '/opt/datadog-agent/embedded/bin/python3'

NOTE: this PR requires version agent 7.44.0 or higher for the snowflake integration to work

Description of the Change

Alternate Designs

Possible Drawbacks

Verification Process

Additional Notes

Release Notes

Review checklist (to be filled by reviewers)

• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have one changelog/ label attached. If applicable it should have the backward-incompatible label attached.
• PR should not have do-not-merge/ label attached.
• If Applicable, issue must have kind/ and severity/ labels attached at least.