3.2dev branch - correct control IDs and legacy tags

[ejaronne]

To "future-proof", Control IDs and their control filenames should be the prefix of the new STIG Rule ID:

(using https://github.com/mitre/redhat-enterprise-linux-7-stig-baseline/blob/3.2dev/controls/V-204392.rb as an example)

Change "control 'V-204392'" to "control 'SV-204392'"
and
Change V-204392.rb to SV-204392.rb

Also, for consistency as per the style of the RHEL8 profile:

Change:
tag 'legacy_id': 'V-71849'
To:
tag legacy: ['V-71849', 'SV-86473']

Change:
tag rid: 'SV-86473r4_rule'
To:
tag rid: 'SV-204392r603261_rule'

As seen in the STIG viewer: