`StringprepTablesReader` into a model that can be used at runtime.

This format is chosen to make it easy to validate that these tables are consistent with the RFC.

```
cd okhttp/src/test/resources/okhttp3/internal/idn/
ls rfc3454.*.txt | xargs -n 1 -I {} bash -c "echo {} ; cat {}" > okhttp_tables.txt
curl https://www.rfc-editor.org/rfc/rfc3454.txt > rfc3454.txt
diff rfc3454.txt okhttp_tables.txt | less

abeno.osaka.jp abiko.chiba.jp abira.hokkaido.jp abkhazia.su able abo.pa abogado abr.it abruzzo.it abu.yamaguchi.jp abudhabi ac ac.ae ac.at ac.be ac.ci ac.cn ac.cr ac.cy ac.fj ac.gn ac.gov.br ac.id ac.il ac.im ac.in ac.ir ac.jp ac.ke ac.kr ac.leg.br ac.lk ac.ls ac.ma ac.me ac.mu ac.mw ac.mz ac.ni ac.nz ac.pa ac.pr ac.rs ac.ru ac.rw ac.se ac.sz ac.th ac.tj ac.tz ac.ug ac.uk ac.vn ac.za ac.zm ac.zw aca.pro academia.bo academy academy.museum accenture accesscam.org accident-investigation.aero accident-prevention.aero...

app_path=$0

# Need this for daisy-chained symlinks.
while
    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
    [ -h "$app_path" ]
do
    ls=$( ls -ld "$app_path" )
    link=${ls#*' -> '}
    case $link in             #(
      /*)   app_path=$link ;; #(
      *)    app_path=$APP_HOME$link ;;
    esac
done

# This is normally unused
# shellcheck disable=SC2034

// Submitted by registry <******@****.***>
lr
com.lr
edu.lr
gov.lr
org.lr
net.lr

// ls : http://www.nic.ls/
// Confirmed by registry <lsadmin@nic.ls>
ls
ac.ls
biz.ls
co.ls
edu.ls
gov.ls
info.ls
net.ls
org.ls
sc.ls

// lt : https://en.wikipedia.org/wiki/.lt
lt
// gov.lt : http://www.gov.lt/index_en.php
gov.lt

10798         ; mapped                 ; 0284          # 14.0 MODIFIER LETTER SMALL DOTLESS J WITH STROKE AND HOOK
10799         ; mapped                 ; 02AA          # 14.0 MODIFIER LETTER SMALL LS DIGRAPH
1079A         ; mapped                 ; 02AB          # 14.0 MODIFIER LETTER SMALL LZ DIGRAPH
1079B         ; mapped                 ; 026C          # 14.0 MODIFIER LETTER SMALL L WITH BELT