Document that DuckDB extension installs need a HOME directory

[ferruzzi]

DuckDB installs extensions under the user's home directory and fails with "IO Error: Can't find the home directory" when HOME is unset or empty, which is the default state of an AWS Lambda function. Providing a writable home directory is part of configuring the environment rather than something the provider can guess, since any directory it picked would be discarded when the task exits and so would re-download every extension.

Document the requirement in the DuckDB connection docs, in the Amazon DuckDB operator docs where the two S3 extensions are installed by default, and in the Lambda executor docs. Set HOME in the Lambda reference Dockerfile beside the existing AIRFLOW_HOME, which is the same /tmp constraint.

Checked against duckdb 1.2.0, 1.3.0, 1.3.2, 1.4.0, 1.4.1, 1.5.0 and 1.5.5: an install fails on every version without a usable HOME, extension_directory stops covering for a missing HOME at 1.5.0, and loading a pre-populated extension_directory with autoinstall_extensions disabled works everywhere.

Follow-up instead of #74126

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