rework server bootstrap completion

[MichaelBrim]

Description

• replace server pids pthread mutex/cond with ABT versions
• add margo_state_dump() on client-server or server-server failures (currently commented out)
• add a 'bootstrap complete' broadcast rpc after rank 0 sees all servers have reported
• fix function declaration for unifyfs_invoke_broadcast_extents()

Motivation and Context

Flash-X on OLCF Summit was consistently failing to bootstrap at 12 nodes. Some of the servers were ready for client connections while others were still in the bootstrap phase.

Previously, servers assumed a successful "server bootstrap" phase when they received a response to the RPC used to report their pid to rank 0. These changes ensure that every server reaches consensus on bootstrap completion before we generate the unifyfs_server.pids file that is used by the command-line utility to report success in a user job.

How Has This Been Tested?

Tested on OLCF Summit. Getting to a working config required use of margo 0.13.1, mercury 2.2, argobots 1.1, and libfabric 1.14.1

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Testing (addition of new tests or update to current tests)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the UnifyFS code style requirements.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All commit messages are properly formatted.