Pull request: * all: move internal Go packages to internal/

Merge in DNS/adguard-home from 2234-move-to-internal to master

Squashed commit of the following:

commit d26a288cabeac86f9483fab307677b1027c78524
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Fri Oct 30 12:44:18 2020 +0300

    * all: move internal Go packages to internal/

    Closes #2234.

internal/isdelve/delve.go

@@ -0,0 +1,5 @@
+// +build delve
+
+package isdelve
+
+const Enabled = true

internal/isdelve/doc.go

@@ -0,0 +1,3 @@
+// Package isdelve is for checking if we're debugging:
+// https://stackoverflow.com/questions/47879070/how-can-i-see-if-the-goland-debugger-is-running-in-the-program
+package isdelve

internal/isdelve/nodelve.go

@@ -0,0 +1,5 @@
+// +build !delve
+
+package isdelve
+
+const Enabled = false