Non-unique variable names within a container

The Variables type does not specify that its name should be unique within a cotainer, but it seems that DAP assumes that they are in several places:

• At least some implementations fail to list repeated names in a Variables response. (Related https://github.com/microsoft/vscode/issues/107506)
• SetVariables request takes a name argument, which produces ambiguity (and leaves some vars inaccessible) if there are multiple variables of that name
• I'm not using Data Breakpoints yet, but DataBreakpointInfo also seems to use ref+name to identify a variable, with the same problems as SetVariables

This is causing some problems for me, because in Lua it's perfectly valid to do something like this:

local function a()
  local a = 1
  local a = 2
  local a = 3
  local a = 4
  return
end

or

local function a()
  local a = 1
  do
    local a = 2
    print(a) -- uses the second a
  end
  print(a) -- uses the first a again
end

and I've had some complaints from users about getting "the wrong" version of redefined locals.

It seems like the protocol wants me to make a new Scope at every block or something like that, but i don't get enough information from the Lua runtime to do that, and in any case it wouldn't work since redefining within a block is legal anyway.