equality of elements of submodules of the same module

Nobody has claimed this yet.

Given two submodules M and N in a free module F, if I have elements m in M and n in N, what should m == n check? Currently, this is automatically false if M and N are not the same, but I think given that both are submodules of the same free module F, they should be equal, no? Here is an example:
```m2
R = kk[x,y]
M = image matrix {{x,0}, {0,y}}
N = image matrix {{0,x}, {y,0}}

-- As vectors:
M_0 == N_1 -- false, but I think this should be true
M_0 === N_1 -- false, which is fine

-- As matrices:
M_{0} == N_{1} -- true
M_{0} === N_{1} -- false, which is fine
```

If these vectors are considered equal, this would also be true:
```m2
debug needsPackage "FGLM"
I = cyclic(5)
M = module I
N = module ideal random I_*
S1 = set M_*
S2 = set N_*
S1 == S2 -- false

L1 = set apply(5, i -> image N_{i})
L2 = set apply(5, i -> image M_{i})
L1 == L2 -- true
```

---

Unrelated, but GC just crashed my M2 while I was comparing two vectors above:
```m2
i183 : M = image matrix {{x,0}, {0,y}}

o183 = image | x 0 |
| 0 y |

2
o183 : R-module, submodule of R

i184 : N = image matrix {{0,x}, {y,0}}

o184 = image | 0 x |
| y 0 |

2
o184 : R-module, submodule of R

i185 : M_0 == N_1

o185 = false

i186 : M_0 === N_1 -- M2 got stuck here so I interrupted it after a second
C-c C-c C-c C-c
Exit (y=yes/n=no/a=abort/b=backtrace)? b
-* stack trace, pid: 628252
0# profiler_stacktrace(std::ostream&, int) at /home/mahrud/Projects/M2/quickfix/M2/Macaulay2/bin/main.cpp:131
1# interrupt_handler at /home/mahrud/Projects/M2/quickfix/M2/Macaulay2/bin/main.cpp:285
2# 0x0000000000019C30 in /lib64/libc.so.6
3# GC_mark_from in /home/linuxbrew/.linuxbrew/opt/bdw-gc/lib/libgc.so.1
4# GC_mark_local in /home/linuxbrew/.linuxbrew/opt/bdw-gc/lib/libgc.so.1
5# GC_mark_some in /home/linuxbrew/.linuxbrew/opt/bdw-gc/lib/libgc.so.1
6# GC_stopped_mark in /home/linuxbrew/.linuxbrew/opt/bdw-gc/lib/libgc.so.1
7# GC_try_to_collect_inner in /home/linuxbrew/.linuxbrew/opt/bdw-gc/lib/libgc.so.1
8# GC_grow_table in /home/linuxbrew/.linuxbrew/opt/bdw-gc/lib/libgc.so.1
9# GC_register_finalizer_inner in /home/linuxbrew/.linuxbrew/opt/bdw-gc/lib/libgc.so.1
10# pthread0_newThreadRWLock at /home/mahrud/Projects/M2/quickfix/M2/Macaulay2/d/pthread0.d:50
11# hashtables_copy at /home/mahrud/Projects/M2/quickfix/M2/Macaulay2/d/hashtables.dd:298
12# override_2 at /home/mahrud/Projects/M2/quickfix/M2/Macaulay2/d/actors3.d:82
13# evaluate_evalraw at /home/mahrud/Projects/M2/quickfix/M2/Macaulay2/d/evaluate.d:1435
14# evaluate_evalSequence at /home/mahrud/Projects/M2/quickfix/M2/Macaulay2/d/evaluate.d:461
```

Reproduce the M and N equality examples first, then inspect the reported stack trace through main.cpp, pthread0.d, hashtables.dd, actors3.d, and evaluate.d. Determine the intended distinction between == and === for elements of submodules, and verify that the equality checks complete without the reported GC hang.

Written by the indexing model from the issue text.