first off, we add an oddly slow basic test of 10k item inventory
Before:
```
Ran 229 tests in 13.214s
OK
real 0m13.403s
user 0m12.106s
sys 0m1.155s
```
After:
```
Ran 230 tests in 21.328s
OK
real 0m21.516s
user 0m20.099s
sys 0m1.275s
```
since that seems like a bit long for the test to add to runtime, lets profile
`python -m cProfile -s time ./bin/ansible all -i test/units/inventory_test_data/huge_range --list-hosts`
Before:
```
1272607 function calls (1259689 primitive calls) in 8.497 seconds
Ordered by: internal time
ncalls tottime percall cumtime percall filename:lineno(function)
10000 4.393 0.000 4.396 0.000 __init__.py:395(_get_host)
20000 2.695 0.000 2.697 0.000 __init__.py:341(__append_host_to_results)
40369 0.113 0.000 0.113 0.000 {posix.lstat}
50006 0.102 0.000 0.153 0.000 __init__.py:1490(combine_vars)
40008 0.089 0.000 0.202 0.000 __init__.py:1546(_load_vars_from_path)
20195 0.088 0.000 0.088 0.000 {posix.stat}
10011 0.087 0.000 0.087 0.000 {posix.getcwd}
```
The top two lines are promising optimization targets
- populate Inventory's host cache more in _get_host, as we are looping
over all the groups anyways.
- eliminate duplicate check of whether we've already included a host
in the construction around __append_host_to_results we can infer
presence of a host in the results list implies the presence of its
name in the hostnames set, allowing us to only to the less expensive
of the two checks
After:
```
1252610 function calls (1239692 primitive calls) in 1.320 seconds
Ordered by: internal time
ncalls tottime percall cumtime percall filename:lineno(function)
40369 0.105 0.000 0.105 0.000 {posix.lstat}
50006 0.094 0.000 0.141 0.000 __init__.py:1490(combine_vars)
40008 0.081 0.000 0.184 0.000 __init__.py:1546(_load_vars_from_path)
10011 0.080 0.000 0.080 0.000 {posix.getcwd}
20195 0.074 0.000 0.074 0.000 {posix.stat}
10002 0.069 0.000 0.261 0.000 __init__.py:1517(load_vars)
```
* Speed up serialization of hostvars by simply using the internal
dictionary used for cached lookups
* Use blocking gets/puts on queues instead of spin locking
* Merge sequential implicitly created blocks
