[SPARK-30994][CORE][FOLLOWUP] Add core dep for xerces 2.12.0

[srowen]

What changes were proposed in this pull request?

Add direct xerces dependency in core.
Follow up of #27746

Why are the changes needed?

Ensures SBT build picks up the updated dep.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Existing tests.

[SparkQA]

Test build #119302 has finished for PR 27790 at commit 05f478d.

• This patch fails build dependency tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #119304 has finished for PR 27790 at commit 7f9e801.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dongjoon-hyun]

Retest this please.

[SparkQA]

Test build #119326 has finished for PR 27790 at commit 7f9e801.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

@tgravescs this failed but not for the same reason - let me retest to see if it reproduces the error you see.

[srowen]

Jenkins retest this please

[tgravescs]

ok, yeah if you have a build against Hadoop-2.7 just try starting the spark master ./sbin/start-master.sh and if you don't see it let me know.

[SparkQA]

Test build #119333 has finished for PR 27790 at commit 7f9e801.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

Jenkins, retest this please

[srowen]

Closed in favor of #27808

[SparkQA]

Test build #119391 has finished for PR 27790 at commit 7f9e801.

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