runLengthEncode rewrite

[pzinn]

this is a complete rewrite of the code in runLengthEncode.
I've also taken the opportunity to merge rle and runLengthEncode.
The behaviour should be mostly unchanged, except for a few extra Holders here and there for consistency and to fix obscure cases of the documented value behaviour.
And it fixes #4393. Repeated entries are encoded before consecutive entries. A range is encoded only when it has three entries or more. Tests added.
(There was already one related test in normal/formatting.m2 but I decided to leave it there and create a new test file.)

[pzinn]

there are two failing examples:

• one is easy, [x..y] should become [x,y]
• the other is more problematic: currently [s_(1,1), s_(1,2), s_(2,1), s_(2,2)] becomes [s_(1,1)..s_(2,2)] which seems good to me. but after the PR we don't create ranges of length 2...

edited: all good now, first example corrected, and fixed code so second example unchanged

[d-torrance]

The following WeylAlgebras test is failing:

i14 : 
        -- Dbasics basics
        R = QQ[r,s];

i15 :   A = makeWeylAlgebra R;

i16 :   B = QQ[r,s,dr,ds,WeylAlgebra => {r=>dr,s=>ds}];

i17 :   assert (describe A===describe B);
stdio:22:8:(3):[1]: error: assertion failed

They look the same, but from what I can tell, the r, dr, s, and ds in the WeylAlgebra => {{r,dr}, {d,ds}} option below are now coming from different monoids:

i5 : describe A

o5 = QQ[r, s, dr, ds, Degrees => {4:1}, Heft => {1}, WeylAlgebra => {{r, dr}, {s, ds}}]

i6 : describe B

o6 = QQ[r, s, dr, ds, Degrees => {4:1}, Heft => {1}, WeylAlgebra => {{r, dr}, {s, ds}}]

i7 : rA = (describe A)#0#1#6#2#0#0#0#0

o7 = r

o7 : monoid[r, s, dr, ds, Degrees => {4:1}, Heft => {1}, WeylAlgebra => {{r, dr}, {s, ds}}]

i8 : rB = (describe B)#0#1#6#2#0#0#0#0

o8 = r

o8 : monoid[r, s, dr, ds, Degrees => {4:1}, Heft => {1}, WeylAlgebra => {{r, dr}, {s, ds}}]

i9 : rA === rB

o9 = false

i10 : hash class rA

o10 = 1044676

i11 : hash class rB

o11 = 1044700

[pzinn]

yeah that's a weird one. will investigate

[pzinn]

edited: figured it out. the modification of runLengthEncode modified the describe of a Weyl algebra -- there shouldn't be a monoid element in the description. should be an easy fix.

[seangrate]

The added tests are appreciated!