sys-apps/portage: Bump to version 2.3.100

sys-apps/portage: Bump to version 2.3.100

 #715108 Change default BINPKG_COMPRESS to zstd
 #719456 Add dependency on app-arch/zstd
 #720866 Do not set PKG_CONFIG_PATH
 #721402 Hostname UnicodeEncodeError surrogates not allowed
 #721516 Suppress precompressed QA notice for docompress -x

Bug: https://bugs.gentoo.org/721152
Bug: https://bugs.gentoo.org/715108
Bug: https://bugs.gentoo.org/719456
Bug: https://bugs.gentoo.org/720866
Bug: https://bugs.gentoo.org/721402
Bug: https://bugs.gentoo.org/721516
Package-Manager: Portage-2.3.100, Repoman-2.3.22
Signed-off-by: Zac Medico <zmedico@gentoo.org>