terminal/starbind: fix starlark conversion of named consts

[arvidfm]

If a value of a derived integer type matches a named constant, Delve will wrap the string representation of the value with the name of the constant, causing ParseInt/ParseUint to fail. This change removes the wrapping before attempting to parse the value before sending it to Starlark.

Fixes #3801

[aarzilli]

LGTM but it would be better with a regression test. Tests for starlark go in pkg/terminal/starlark_test.go and _fixture/consts.go can be used for enums. If I understand correctly this test it could be enough to write this:

func TestStarlarkEnumValue(t *testing.T) {
	withTestTerminal("consts", t, func(term *FakeTerminal) {
		term.MustExec("continue")
		out := strings.TrimSpace(term.MustExecStarlark(`v = eval(None, "a"); print(v.Value)`))
		if out != "2" {
			t.Fatalf("expected 2 got %s", out)
		}
	})
}

[arvidfm]

@aarzilli Since there was already an existing test specifically for testing the results of expressions I figured it made sense to add the test cases there and the associated fixture, but let me know if you'd prefer me to move them to their own test

[aarzilli]

LGTM

[derekparker]

LGTM