Improve diagnostics for unclosed strings, heredocs, atoms and sigils

[viniciusmuller]

Elixir and Erlang/OTP versions

main

Operating system

any

Current behavior

• Unclosed atoms with string content

a = :"Elixir.UnclosedModule

String.to_atom(a)

• Unclosed heredocs

a = """
test string

IO.inspect(10 + 20)

• Unclosed sigils

a = ~s[test string
[IO.inspect(10 + 20)

IO.inspect(a)

• Unclosed strings

a = "test string

IO.inspect(10 + 20)

Expected behavior

Formatting similar to the 'unclosed delimiter' diagnostic for these cases