[WIP] Try to filter test items without constructing the AST

[Drvi]

@btime (try runtests("test", failures_first=true, name="aaa") catch end) # in RAICode, 7,1 threads

 master:    175.964 ms (2881429 allocations: 226.19 MiB)
 #225:      101.575 ms (2823433 allocations: 219.54 MiB)
 #225 + PR:  52.763 ms (1023628 allocations: 68.09 MiB)

This also means we're not validating every test item on every run -- only those that match the name will be evaluated.

[nickrobinson251]

we can't (don't want) any non-stdlib deps... how much benefit does StringViews give us? Our options are (i think): drop it, reimplement a minimal version, vendor it

[nickrobinson251]

this we'd probably have to vendor