Clarify BoundedCapacity operations

### Type of issue

Missing information

### Description

Please clarify the documentation to answer the following questions:
1. Does ```BoundedCapacity``` control an input buffer (before the block processes the item) or output buffer (after the block has processed the item and wants to pass results to the next block)?
2. What happens when there is an attempt to exceed ```BoundedCapacity```? Is the message dropped, does processing paruse, or is an exception thown?

Thanks!

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.threading.tasks.dataflow.dataflowblockoptions.boundedcapacity?view=net-8.0

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.Threading.Tasks.Dataflow/DataflowBlockOptions.xml

### Document Version Independent Id

d940df1c-bcc8-661f-3438-9f5899c1c2cd

### Article author

@dotnet-bot