(MODULES-11011) extend vg facts

[atsonkov]

Adds facts for the extends in the volume groups (size, count, free extends)
Also sets the units to megabytes (of 1024k)
Otherwise the --nosuffix option was not used, and we could get results like '<54,24g'

Ref: MODULES-11011

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[codecov-io]

Codecov Report

Merging #261 (9265b6f) into master (cada6d4) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 9265b6f differs from pull request most recent head ef7f9d1. Consider uploading reports for the commit ef7f9d1 to get more accurate results

@@           Coverage Diff           @@
##           master     #261   +/-   ##
=======================================
  Coverage   72.96%   72.96%           
=======================================
  Files          17       17           
  Lines         773      773           
=======================================
  Hits          564      564           
  Misses        209      209           

Impacted Files	Coverage Δ
lib/facter/volume_groups.rb	100.00% <100.00%> (ø)
lib/facter/lvm_support.rb	73.52% <0.00%> (-2.95%)	⬇️
lib/facter/physical_volumes.rb	100.00% <0.00%> (+11.11%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update cada6d4...ef7f9d1. Read the comment docs.

[atsonkov]

There are 7 CI tests failing for puppet 6, but the same tests are alos failing on master (not affected vy my changes).

Opened separate issue for fixing master (MODULES-11016).