refactor(EncodingConverter): remove deprecated conversion methods and…

[SHIINASAMA]

… simplify implementation

[github-actions]

Package	Line Rate	Branch Rate	Health
sese.archive	86%	67%	✔
sese.concurrent	100%	100%	✔
sese.config	88%	72%	✔
sese.config.ini	94%	75%	✔
sese.config.xml	100%	91%	✔
sese.container	100%	69%	✔
sese.convert	100%	96%	✔
sese.db	100%	96%	✔
sese.internal.db.maria	87%	70%	✔
sese.internal.db.pgsql	83%	70%	✔
sese.internal.db.sqlite	88%	70%	✔
sese.internal.net	100%	100%	✔
sese.internal.net.http	61%	47%	➖
sese.internal.service.dns	34%	16%	❌
sese.internal.service.http	70%	38%	➖
sese.internal.unix.system	98%	71%	✔
sese.io	97%	83%	✔
sese.native.linux.system	97%	75%	✔
sese.native.unix.config	100%	100%	✔
sese.native.unix.net	95%	55%	✔
sese.native.unix.security.evp	100%	100%	✔
sese.native.unix.system	90%	75%	✔
sese.native.unix.thread	100%	100%	✔
sese.net	97%	95%	✔
sese.net.dns	84%	49%	✔
sese.net.http	80%	71%	✔
sese.net.ws	100%	100%	✔
sese.plugin	79%	50%	➖
sese.record	75%	66%	➖
sese.res	100%	97%	✔
sese.security	98%	90%	✔
sese.security.evp	100%	100%	✔
sese.service	82%	54%	✔
sese.service.dns	64%	32%	➖
sese.service.http	80%	48%	✔
sese.service.iocp	69%	64%	➖
sese.system	84%	48%	✔
sese.text	91%	67%	✔
sese.thread	99%	80%	✔
sese.util	88%	68%	✔
Summary	86% (7926 / 9249)	61% (4367 / 7164)	✔

Minimum allowed line rate is 60%