[SPARK-56270][PYTHON] Fix type hints and import issue for find_spark_home

[gaogaotiantian]

What changes were proposed in this pull request?

• Remove the type hint ignore for find_spark_home module and fill in the type hints
• Remove the ImportError check and import_error_raised related logic

Why are the changes needed?

There's no reason we can't type hint this module so I just did it.

For the import part, it's impossible to trigger that path because find_spec("pyspark") will never trigger ImportError. It either returns a spec or None. I searched the history and the first time it was introduced was in #15659 . There were 2 branches and the one for python2 actually will trigger the ImportError. The python3 branch won't work but it might just be ignored.

In #28152 we added import_error_raised check and extra messages, but we only tested in python2, which would trigger that message. I confirmed that the message won't be printed if we can't find pyspark.

Now we print the message if we can't find SPARK_HOME.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Locally confirmed the message will be printed if pyspark can't be imported. Lint also passed locally.

Was this patch authored or co-authored using generative AI tooling?

No.