Comment 1 for bug 1931162

Branch is available here for testing:

https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/miker/lp-1931162-DYM-optimization / user/miker/lp-1931162-DYM-optimization

From the commit:

For some data sets and some queries the Did You Mean search suggestion logic can be much too slow. This is mainly in cases where a "misspelled" word of sufficient length greater than the symspell prefix length is checked against many short prefixes that have many long suggestions attached to them.

This commit optimizes for that case in particular by testing the length of suggestions and prefix keys against the user input to avoid unnecessary tests. Futher, it captures the edit distance of suggestions that pass that test in-line, avoiding expensive retesting, and caches the short-cutoff edit distance when in low-verbosity mode to avoid future different-but-not-too-different suggestions coming from the same prefix key.

It additionally provides a general optimization by batching the capture of suggest counts to avoid per-suggestion secondary lookups, and a micro-optimization of ordering suggestions by length at distance cache time.