Adds functions for checking the type of variables

[udondan]

Fixes #23070 <- Description and use case can be found in that issue.

PR covers

• Functionality (79 lines)
• Tests (263 lines)
• Documentation (441 lines)

My Terraform test code:

locals {
  bool   = false
  list   = list(1, 2, 3)
  map    = map("foo", 112)
  number = 6
  object = { foo : "bar" }
  set    = set(1, 2, 5)
  string = "foo"
  tuple  = [1, 2, 3]
}

output "type" {
  value = {
    bool   = type(local.bool)
    list   = type(local.list)
    map    = type(local.map)
    null   = type(null)
    number = type(local.number)
    object = type(local.object)
    set    = type(local.set)
    string = type(local.string)
    tuple  = type(local.tuple)
  }
}
output "is" {
  value = {
    bool   = isbool(local.bool)
    list   = islist(local.list)
    map    = ismap(local.map)
    null   = isnull(null)
    number = isnumber(local.number)
    object = isobject(local.object)
    set    = isset(local.set)
    string = isstring(local.string)
    tuple  = istuple(local.tuple)
  }
}

output "isNot" {
  value = {
    bool   = isbool(local.number)
    list   = islist(local.map)
    map    = ismap(local.list)
    null   = isnull(local.number)
    number = isnumber(null)
    object = isobject(local.set)
    set    = isset(local.object)
    string = isstring(local.tuple)
    tuple  = istuple(local.string)
  }
}

Applying above code results in this output:

Apply complete! Resources: 0 added, 0 changed, 0 destroyed.

Outputs:

is = {
  "bool" = true
  "list" = true
  "map" = true
  "null" = true
  "number" = true
  "object" = true
  "set" = true
  "string" = true
  "tuple" = true
}
isNot = {
  "bool" = false
  "list" = false
  "map" = false
  "null" = false
  "number" = false
  "object" = false
  "set" = false
  "string" = false
  "tuple" = false
}
type = {
  "bool" = "bool"
  "list" = "list"
  "map" = "map"
  "null" = "null"
  "number" = "number"
  "object" = "object"
  "set" = "set"
  "string" = "string"
  "tuple" = "tuple"
}

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