[SPARK-3873] [build] Enable import ordering error checking.

[vanzin]

Turn import ordering violations into build errors, plus a few adjustments
to account for how the checker behaves. I'm a little on the fence about
whether the existing code is right, but it's easier to appease the checker
than to discuss what's the more correct order here.

Plus a few fixes to imports that cropped in since my recent cleanups.

[vanzin]

I'll let this simmer for a few days to wait for new PRs that might have violations to go in, and fix those... but at some point I'll get bored of fixing things and probably push this.

[SparkQA]

Test build #48816 has finished for PR 10612 at commit 1f08d6e.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[vanzin]

retest this please

[SparkQA]

Test build #48834 has finished for PR 10612 at commit 930ccd3.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #48862 has finished for PR 10612 at commit 35569f9.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

you'd need to remove this line

[SparkQA]

Test build #48888 has finished for PR 10612 at commit 6da306d.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

LGTM.

[rxin]

You should probably just find a slow day (Sat night / Sun morning?) to bring this up to date and merge it.

[vanzin]

Will probably do that Monday morning (or Sunday evening if I'm feeling bored).

[SparkQA]

Test build #49077 has finished for PR 10612 at commit 782f6de.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #49081 has finished for PR 10612 at commit 2226c9d.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

I've merged this. Thanks.