Fix OpenHarmony's tzdata parsing

[ldm0]

OpenHarmony's tzdata parsing supported was introduced in #1613.

OpenHarmony's tzdata shares the same characters with the ones on Android, except that each timezone index is 4 byte's smaller(the legacy rawUtcOffset was removed).

OpenHarmony's tzdata
Android's tzdata

As their parsing logic are pretty similar, I unified their logic into src/offset/local/tzdata.rs(I actually created a crate for that, but the logic is simple enough to put into chrono). This also allows us to remove the android_tzdata dependency.

BTW, OpenHarmony's tzdata parsing logic was also added in fallback_timezone, that's because OpenHarmony doesn't have /etc/localtime, people need to use it's time service api to get the timezone name. I created a PR for iana-time-zone to support OpenHarmony's timezone name fetching: strawlab/iana-time-zone#150. After getting the timezone name from iana_time_zone::get_timezone, chrono need to find it's timezone information in the tzdata.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.67%. Comparing base (39fb201) to head (15a9940).
Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1679      +/-   ##
==========================================
- Coverage   91.08%   90.67%   -0.41%     
==========================================
  Files          37       39       +2     
  Lines       17469    17070     -399     
==========================================
- Hits        15912    15479     -433     
- Misses       1557     1591      +34     

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[djc]

This should come with CI coverage for Android and OpenHarmony. The new parser should be cleaned up, have a look at the rustls style guide (which I wrote) and try to simplify (drop the OS constructor, make the constant names more concise, avoid nested types/functions).

[ldm0]

@djc Hi, all new lines are covered now, and parser was cleaned up. Please take a look.