NFD

https://gerrit.named-data.net/5399 eliminates Selectors from CS tests; it also promotes FindFixture to CsFixture for simplifying CS policy tests.

Rationale for changes in TestCs/Find suite:

• EmptyInterestName: deleting because zero-component Interest name is forbidden by spec
• ExactName: spliting to ExactName (CanBePrefix=false) and ExactName_Cbp (CanBePrefix=true)
• EmptyDataName: changing to FullName_EmptyDataName with implicit digest included in Interest name, because zero-component Interest name is forbidden by spec
• Leftmost: renaming to PrefixName and adding CanBePrefix=true; also creating PrefixName_NoCbp with CanBePrefix=false
• Rightmost, MinSuffixComponent, MaxSuffixComponent, DigestOrder, DigestExclude: deleting because Selectors are gone

https://gerrit.named-data.net/5402 stops processing ChildSelector in CS implementation. It also converts some function objects into template arguments for better performance.
Processing of other Selectors comes from Interest::matchesData that belongs to #4913.

Currently, I'm simply removing ChildSelector processing without further optimization.
I recognize the opportunity of reducing "prefix range" when CanBePrefix is unset, but I'd defer that to #4914.

From https://gerrit.named-data.net/5402:

code is fine but this should be merged after #4916

I disagree. According to 0.6.5 release notes:

Note that this is the last release that encodes to NDN packet format version 0.2.1. A future release will continue to decode v0.2.1 format, but will encode to v0.3 format.

There's no need to wait for any more releases.