[SPARK-22696][SQL] objects functions should not use unneeded global variables

[mgaido91]

What changes were proposed in this pull request?

Some objects functions are using global variables which are not needed. This can generate some unneeded entries in the constant pool.

The PR replaces the unneeded global variables with local variables.

How was this patch tested?

added UTs

[SparkQA]

Test build #84548 has finished for PR 19908 at commit a33bd99.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
• case class ReqAndHandler(req: Request, handler: MemberHandler)
• trait TypeCoercionRule extends Rule[LogicalPlan] with Logging
• case class AnalysisBarrier(child: LogicalPlan) extends LeafNode

[mgaido91]

@cloud-fan @kiszk @viirya may you please review this? Thanks

[SparkQA]

Test build #84571 has finished for PR 19908 at commit e7cdbd7.

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

[viirya]

LGTM

[cloud-fan]

thanks, merging to master!