Cherry pick several changes back from 1.19.3

The main purpose of this is to backport the improved parse/runtime
errors to older versions. I think they're sufficiently useful that we
should try to make it as widely available as possible.

We've been running them for a week now on SC3 and the released version
and not seen any issues, so I think it's probably stable enough.

This is a pretty lazy commit: I ended up copying the whole ROM over and
then picking up a few other related changes along the way.

 - Trim spaces from file paths (b8fce1eecc)

 - Correctly format 12AM/PM with
   %I (9f48395596)

 - Fix http.request and htpt.websocketAsync not handling a few failure
   edge-cases correctly (3b42f22a4f).

 - Move the internal modules into the main package path, hidden under
   cc.internal (34a31abd9c).

 - Gather code coverage in Java instead of
   Lua (28a55349a9).

 - Make error messages in edit more
   obvious (8cfbfe7ceb).

 - Make mcfly's test methods global. This means we don't need to pass
   stub everywhere (7335a892b5).

 - Improve runtime and parse errors. This comes from numerous commits,
   but chiefly a12b405acf, and
   5502412181.

 - Hide the internal redirect methods in
   multishell (33b6f38339).

Note this does /not/ include the shebang changes (sorry Emma!). I've
tried to avoid adding any user-controllable features, mostly because I
don't know how to handle the versioning otherwise :).

src/test/resources/test-rom/spec/programs/alias_spec.lua

@@ -2,27 +2,27 @@ local capture = require "test_helpers".capture_program
 
 describe("The alias program", function()
     it("displays its usage when given too many arguments", function()
-        expect(capture(stub, "alias a b c"))
+        expect(capture("alias a b c"))
             :matches { ok = true, output = "Usage: alias <alias> <program>\n", error = "" }
     end)
 
     it("lists aliases", function()
         local pagedTabulate = stub(textutils, "pagedTabulate", function(x) print(table.unpack(x)) end)
         stub(shell, "aliases", function() return { cp = "copy" } end)
-        expect(capture(stub, "alias"))
+        expect(capture("alias"))
             :matches { ok = true, output = "cp:copy\n", error = "" }
         expect(pagedTabulate):called_with_matching({ "cp:copy" })
     end)
 
     it("sets an alias", function()
         local setAlias = stub(shell, "setAlias")
-        capture(stub, "alias test Hello")
+        capture("alias test Hello")
         expect(setAlias):called_with("test", "Hello")
     end)
 
     it("clears an alias", function()
         local clearAlias = stub(shell, "clearAlias")
-        capture(stub, "alias test")
+        capture("alias test")
         expect(clearAlias):called_with("test")
     end)
 end)