Clean up cputopology initialization global communication pattern

[evan-charmworks]

• Replaces error-prone locking and improper scheduler driving with well-tested pattern from Isomalloc-Sync
• Replaces bespoke "empty reduction" with CmiBarrier
• Replaces Broadcast with NodeBroadcast and moves send outside of handler
• Replaces unnecessary privatization of Converse handler index variables with CmiAssignOnce

[evan-charmworks]

@trquinn Does this resolve the hang on init from #2850?

[evan-charmworks]

Spurious and unrelated:

/Applications/Xcode_12.4.app/Contents/Developer/usr/bin/make -C method_templates smptest OPTS='-g -build-shared -optimize -production' TESTOPTS='++local +setcpuaffinity'
########################################################################################
../../../bin/testrun   +p4 ./testTemplateEP  ++ppn 2 ++local +setcpuaffinity
Charmrun> scalable start enabled. 
Charmrun> started all node programs in 0.017 seconds.
Charm++> Running in SMP mode: 2 processes, 2 worker threads (PEs) + 1 comm threads per process, 4 PEs total
Charm++> The comm. thread both sends and receives messages
Converse/Charm++ Commit ID: 264b00b
Isomalloc> Synchronized global address space.
Charm++> scheduler running in netpoll mode.
CharmLB> Load balancer assumes all CPUs are same.
sched_setaffinity() is not supported, +setcpuaffinity disabled.
Charm++> Running on 1 hosts (1 sockets x 3 cores x 1 PUs = 3-way SMP)
Charmrun> error on request socket to node 0 '127.0.0.1'--
Socket closed before recv.

real	10m0.184s
user	4m25.177s
sys	4m39.497s
make[3]: *** [smptest] Error 1
make[2]: *** [smptest-method_templates] Error 2
make[1]: *** [test] Error 2
make: *** [test-charm++] Error 2
==> Error: ProcessError: Command exited with status 2:
    'make' '-C' '/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/runner/spack-stage/spack-stage-charmpp-main-hb6ii4az3aa2ry6fozgur65x3u6wplpw/spack-src/tests' 'test' 'TESTOPTS=++local +setcpuaffinity'

4 errors found in build log:
     22985    Charmrun> error on request socket to node 0 '127.0.0.1'--
     22986    Socket closed before recv.
     22987    
     22988    real	10m0.184s
     22989    user	4m25.177s
     22990    sys	4m39.497s
  >> 22991    make[3]: *** [smptest] Error 1
  >> 22992    make[2]: *** [smptest-method_templates] Error 2
  >> 22993    make[1]: *** [test] Error 2
  >> 22994    make: *** [test-charm++] Error 2

See build log for details:
  /var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/runner/spack-stage/spack-stage-charmpp-main-hb6ii4az3aa2ry6fozgur65x3u6wplpw/spack-build-out.txt

[ericjbohm]

Commit comment should note motive for switching from locked Cpv to atomic.

[evan-charmworks]

Commit comment should note motive for switching from locked Cpv to atomic.

Updated.

[evan-charmworks]

Needs one more review.