Improve performance for long strings for nvtext::replace_tokens

[davidwendt]

Description

Improves performance for nvtext::replace_tokens for long strings.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[davidwendt]

Some performance benchmark results

|row_width|num_rows|   Ref Time |   Cmp Time |           Diff |   %Diff |
|---------|--------|------------|------------|----------------|---------|
|   32    |  4096  |  95.488 us | 100.999 us |       5.512 us |   5.77% |
|   64    |  4096  | 120.956 us | 126.934 us |       5.979 us |   4.94% |
|   128   |  4096  | 193.513 us | 225.669 us |      32.156 us |  16.62% |
|   256   |  4096  | 321.329 us | 232.318 us |     -89.011 us | -27.70% |
|   512   |  4096  | 594.923 us | 269.090 us |    -325.833 us | -54.77% |
|  1024   |  4096  |   1.155 ms | 342.871 us |    -812.532 us | -70.32% |
|   32    | 32768  | 117.734 us | 123.737 us |       6.003 us |   5.10% |
|   64    | 32768  | 164.444 us | 171.198 us |       6.754 us |   4.11% |
|   128   | 32768  | 275.025 us | 333.420 us |      58.395 us |  21.23% |
|   256   | 32768  | 530.392 us | 499.948 us |     -30.444 us |  -5.74% |
|   512   | 32768  |   1.008 ms | 816.931 us |    -190.869 us | -18.94% |
|  1024   | 32768  |   1.856 ms |   1.452 ms |    -404.337 us | -21.78% |
|   32    | 262144 | 307.452 us | 315.685 us |       8.233 us |   2.68% |
|   64    | 262144 | 576.788 us | 583.611 us |       6.823 us |   1.18% |
|   128   | 262144 |   3.243 ms |   1.430 ms |   -1813.488 us | -55.92% |
|   256   | 262144 |   8.539 ms |   2.706 ms |   -5833.149 us | -68.31% |
|   512   | 262144 |  24.445 ms |   5.429 ms |  -19016.762 us | -77.79% |
|  1024   | 262144 |  64.353 ms |  10.712 ms |  -53641.204 us | -83.35% |
|   32    |2097152 |   1.835 ms |   1.841 ms |       5.734 us |   0.31% |
|   64    |2097152 |   4.016 ms |   4.028 ms |      12.260 us |   0.31% |
|   128   |2097152 |  19.600 ms |  10.796 ms |   -8803.548 us | -44.92% |
|   256   |2097152 |  50.128 ms |  21.580 ms |  -28547.777 us | -56.95% |
|   512   |2097152 | 157.250 ms |  44.047 ms | -113202.559 us | -71.99% |
|   32    |16777216|  14.444 ms |  14.421 ms |     -22.290 us |  -0.15% |
|   64    |16777216|  31.994 ms |  31.937 ms |     -56.896 us |  -0.18% |

[bdice]

Looks good to me.

[davidwendt]

/merge