perf: optimize to_char

[kwannoel]

see #7351 (comment).

1. Bench build_to_char_const_tmpl w/o template string. I think what is currently benched includes compilation of template str.
2. Use rust date time formatting as baseline / find some other suitable baseline.
3. Bench date_time::date : perf: nexmark q17 #7351 (comment)
4. Precompute and store in executor the tmpl pattern matching object. This is done already.

[lmatz]

suspect simply because chrono::format::Item is not efficient enough
https://github.com/chronotope/chrono#:~:text=(while%20not%20being%20the%20primary%20goal)%20reasonably%20efficient

[kwannoel]

Update, to_char is not really a performance bottleneck, only ~1% is attributed to it in q17.

However, to_char does lead to things being represented as varchar, which is the real cost.

Opening a separate issue to track.