UCP/API: extend ucp_ep_query for debug info string

[evgeny-leksikov]

What

Add debug info string to ucp_ep_query() API

Why

Show the internal state of the connection, including underlying transport state, for example:

• When the application created new connection
• When the application detected a problem with a connects, such as no progress / "stuck" requests

[yosefe]

@shamisp @tonycurtis can you pls take a look?

[shamisp]

It is a bit vague (from ucp.h documentation) how the debug string used. If the code compiled with debug disabled, does the library still report debug info ?

[shamisp]

@yosefe I'm not sure if this the right way to go for extracting debug information. The debug output string is not standardized and available only within certain build options. The justification for the patch is not very clear - why applications need to know the internal state of connection ? Application developers need this only for debug purpose and there are other tools for this - tracer, etc.