Use fonticons for sorting items on the provisioning form

[skateman]

Go to Lifecycle -> Provision VMs under Virtual Machines, select a template (ideally not an RHV as it requires valid and working credentials) and go to the Environment tab. All the fields that have sortable tables are using these icons for the sortable column's identification.

The image references have been replaced with fa-angle-up and fa-angle-down accordingly and as the PNG files are not used everywhere, I'm removing them.

Parent issue: #4051

@miq-bot add_reviewer @epwinchell
@miq-bot add_label gaprindashvili/no, graphics

[miq-bot]

Checked commits skateman/manageiq-ui-classic@3954540~...b7a61d0 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
10 files checked, 1 offense detected

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• 💣 💥 🔥 🚒 - Linter/Haml - Linter::Haml STDERR:

warning: parser/current is loading parser/ruby23, which recognizes
warning: 2.3.6-compliant syntax, but you are running 2.3.3.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.