[7u] RFR: 8260356: (tz) Upgrade time-zone data to tzdata2021a

[Dmitry Cherepanov]

Bug: https://bugs.openjdk.java.net/browse/JDK-8260356
8u commit: https://hg.openjdk.java.net/jdk8u/jdk8u/jdk/rev/d103481ecd91
7u webrev: http://cr.openjdk.java.net/~dcherepanov/openjdk7u/8260356/webrev.v0/

Applies cleanly after adjusting paths. Relevant regression tests passed.

Thanks,

Dmitry