Deprecate and remove any() and all() functions

[tsandall]

We should deprecate and eventually remove the any() and all() built-in functions. Neither of these functions implement behaviour that's otherwise hard to implement in Rego yet their implementation makes some arbitrary assumptions that are problematic (e.g., non-true/false values are not considered "true-ish" like most other Rego constructs asusme, both are satisfied by empty collections, etc.)

The any function is particularly bad since there is almost no difference between saying any({x | ...}) and simply .... Similarly, once we have the every keyword (#2090) the need for all will be substantially reduced.

[gaga5lala]

Hi @tsandall, does this means to remove built-in ast functions defined in ast/builtins.go and relative files (are they mostly defined in #828?). And then run go test locally (or submit PR wait test result on CI) to check is there any missing pieces?

[patrick-east]

@gaga5lala That is correct, however I'm not sure how soon we would want to make the change. These backwards compatibility changes will need to be handled carefully.

[srenatus]

💭 While we're at it, should we drop and and or as non-infix variants of set intersection & and union |? Those must seem confusing to newcomers.