matrix of exponents instead of monomials from basis

Nobody has claimed this yet.

Is there a fast (i.e. implemented in the engine) routine for the following? (or its transpose)
```m2
exponentMatrix = B -> transpose matrix apply(numcols B, c -> first exponents B_(0,c))

-- example:
i17 : exponentMatrix basis(3, kk[x,y,z])

o17 = | 3 2 2 1 1 1 0 0 0 0 |
| 0 1 0 2 1 0 3 2 1 0 |
| 0 0 1 0 1 2 0 1 2 3 |

3 10
o17 : Matrix ZZ <-- ZZ
```
The one liner above obviously works, but when `B` is a matrix of basis monomials with tens thousands of columns, it gets quite slow (e.g. the basis itself takes a couple of seconds but computing the exponent matrix takes a minute!!)

cc: @mikestillman

Start by locating the engine implementation behind basis and monomial exponent extraction. Compare the existing one-line matrix operation with the requested routine or its transpose, using the issue's example as a correctness check. Done means an implemented routine produces the same exponent matrix and avoids the reported slowdown on bases with tens of thousands of columns.

Written by the indexing model from the issue text.