lib/string: provide `alpha_comparator` and `CachedAlphaComparator`

Sorting alphanumerically has never been so easy.

Signed-off-by: Jean Privat <jean@pryen.org>
model_viz: remove `AlphaComparator`&cie. since thez are now in standard

Signed-off-by: Jean Privat <jean@pryen.org>
rta: add `live_types_to_csv` to provide human-readable info on types

Signed-off-by: Jean Privat <jean@pryen.org>
rta: add `live_methods_to_tree` to provide human-readable infos on methods

Signed-off-by: Jean Privat <jean@pryen.org>
metrics/rta: save the list of live things in files

Simply use `live_types_to_csv` and `live_methods_to_tree` to produce
two files in the correct output directory.

This helps the debugging of engines when RTA is buggy or misused.

Signed-off-by: Jean Privat <jean@pryen.org>
doc: modified comment for typing::AExpr::mtype

Signed-off-by: Alexandre Terrasa <alexandre@moz-code.org>
Merge branch 'dump_rta'