Replace boxing ArrayLists in UIAutomationClientSideProviders (ClickablePoint)

[h3xds1nz]

Description

This should be the last boxing ArrayList that's still left in UIAutomationClientSideProviders when #9388 would be merged.

• Adds System.Collections reference to UIAutomationClientSideProviders to allow for generic collections in the first place.
• Removes two boxing ArrayList instances, both times for CPRect structure in ClickablePoint and ProxySimple class.
• Makes the static fields readonly and moves the other static field init into the static constructor for readability.
• Adjusts the CPRect bool methods as readonly since they do not modify struct state.
• Renames the "al*" params as "list*" to reflect reality this ain't an ArrayList.
• Adjusts internal comments from "Program" to "Progman".

Customer Impact

Improved performance, decreased allocations.

Regression

No.

Testing

Local build.

Risk

Low.

Microsoft Reviewers: Open in CodeFlow

[rchauhan18]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[Kuldeep-MS]

@h3xds1nz - could you please resolve the conflicts

[h3xds1nz]

@Kuldeep-MS Done, sorry for the delay.