[BUG] A bug in the renamer

[konnov]

The following example provokes a bug:

--------------- MODULE Ren ----------------
EXTENDS Integers
VARIABLE n

Foo(k) ==
    LET r(a) == a IN
    n' = r(3)

Init ==
    n = 0

Next ==
    Foo(5)
===========================================

Apparently, this is an artifact of a recent refactoring.

Describe the bug

PASS #7: PreprocessingPass                                        I@21:15:53.471
  > Before preprocessing: unique renaming                         I@21:15:53.471
 > Applying standard transformations:                             I@21:15:53.477
  > Desugarer                                                     I@21:15:53.477
  > UniqueRenamer                                                 I@21:15:53.483
(Please report an issue at: [https://github.com/informalsystems/apalache/issues],java.lang.IllegalArgumentException: Variable names should never contain more than one separator)
Unhandled exception                                               E@21:15:53.485
java.lang.IllegalArgumentException: Variable names should never contain more than one separator
	at at.forsyte.apalache.tla.lir.transformations.standard.IncrementalRenaming$.parseName(IncrementalRenaming.scala:39)
	at at.forsyte.apalache.tla.lir.transformations.standard.IncrementalRenaming$.nameCounterMapFromDecl(IncrementalRenaming.scala:90)
	at at.forsyte.apalache.tla.lir.transformations.standard.IncrementalRenaming$.$anonfun$nameCounterMapFromEx$3(IncrementalRenaming.scala:77)
...

To Reproduce

$ ~/devl/apalache/bin/apalache-mc check Ren.tla

Desktop (please complete the following information):

• Version 0.8.1.