[fuchsia] Updates tzdata revision and path

A cosmetic change that brings the Chromium tests closer to what is
being used in production in Fuchsia today.

- Brings the unit test paths in sync with the correct path in
 Fuchsia:

https://cs.opensource.google/fuchsia/fuchsia/+/master:src/lib/icu/tzdata/icu_tzdata_config_data.gni;l=11

- The loader code in icu_util.cc has been changed before to use the
  correct path, so no changes are required there.

- The content of the tzdata directory is adjusted to match the contents
  that are provided by Fuchsia.  This includes the newly introduced file
  revision.txt, which contains an assertion about what revision of
  tzdata is supposed to be packaged.

Bug: 1139410
Change-Id: I80707a3daa0e492d747e9542b64593bf41a545c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2480891
Reviewed-by: David Dorwin <ddorwin@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Filip Filmar <fmil@google.com>
Cr-Commit-Position: refs/heads/master@{#818994}

base/fuchsia/time_zone_data_unittest.cc

@@ -18,7 +18,7 @@ namespace i18n {
 namespace {
 
 // Directory path to the tzdata configuration files.
-const char kTzDataDirPath[] = "/pkg/base/test/data/tzdata/2019a/44/le";
+const char kTzDataDirPath[] = "/pkg/base/test/data/tzdata/icu/44/le";
 
 // File path to the text file containing the expected ICU library revision, for
 // example "2019c".

base/test/data/tzdata/revision.txt

@@ -0,0 +1 @@
+2019a