change new_teal_data arguments

[gogonzo]

Acceptance criteria:
Constructor method should have variants for a signature data = "list" and data = "environment".

Constructor should work with following call:

new_teal_data(
  data = list(iris2 = iris2),
  code = quote(iris2 <- iris) 
)

new_teal_data(
  data = as.environment(list(iris2 = iris2)),
  code = quote(iris2 <- iris) 
)

[gogonzo]

Closing this PR. new_teal_data will be a private constructor. We will expose teal_data/cdisc_data only.