[New] Create buffers around points

[CalebRas]

Description

This PR implements Create buffers around points in Geometry category.
URL to README: https://github.com/Esri/arcgis-maps-sdk-swift-samples/tree/Caleb/New-CreateBuffersAroundPoints/Shared/Samples/Create%20buffers%20around%20points

Linked Issue(s)

• swift/issues/4100

How To Test

• Tap outside the boundary to see "Tap with the boundary to add buffer" message at the top.
• Tap inside the boundary to add a point.
• Enter a value, such as 100.
• Tap done. (See "Buffer created." message)
• Add another buffer close enough to the first that they will overlap.
• Toggle "Union" on and off to see the buffers merge and un-merge.
• Tap "Clear" to remove all the buffers and points from the map. (See "Tap on the map to add buffers" message.)

Screenshots

[yo1995]

First round of comments.

[des12437]

The documentation reads well, but the style is not consistent with other samples in terms of using code voice to refer to a type. See the documentation in the other samples for reference.

[yo1995]

2nd batch of comments. Good work!