Use const generic for computing min/max

[alamb]

This is a proposed follow on to apache#6089

It makes the exact comparison a const generic so each min and max gets its own specialized version of the code

However, it does not appear to make any difference

alamb@aal-dev:~/arrow-rs$ critcmp const-grater min-max-better-view
group                       const-grater                            min-max-better-view
-----                       ------------                            -------------------
string view/min nonnull     1.00    222.4±0.65µs 281.1 MElem/sec    1.00    222.6±0.51µs 280.8 MElem/sec
string view/min nullable    1.00    205.0±0.64µs 304.9 MElem/sec    1.00    205.1±0.58µs 304.8 MElem/sec
string/min nonnull          1.08    228.8±0.36µs 273.1 MElem/sec    1.00    211.1±0.59µs 296.0 MElem/sec
string/min nullable         1.00    345.6±0.46µs 180.9 MElem/sec    1.00    346.1±0.55µs 180.6 MElem/sec