Presto allows parsing of invalid timezone names

Presto's timezone parsing is too permissive and allows for timezone names that are not valid according to IANA's timezone database, in addition to other bugs:

https://en.wikipedia.org/wiki/List_of_tz_database_time_zones

The following are examples of non-compliant timezone names that are allowed:

ETC/+06:00
ETC/+06
ETC/+6
ETC/UTC*
ETC/UT*

-> the only official formats are "ETC/GMT+1" and similar

EST

-> not supported, but it should be

timezones in the format:

ETC/GMT+10:00

besides not being official, return the wrong result (don't flip the sign as they should)

+1
+01

officially also don't exist (only "+01:00")

Expected Behavior

These should fail to parse, though it might break backwards compatibility.

Current Behavior

They are parsed successfully (incorrectly).

Steps to Reproduce

presto> select from_unixtime(1698528090, 'ETC/+06:00');
             _col0              
--------------------------------
 2023-10-29 03:21:30.000 +06:00 

and other variations described above.

Cc: @mbasmanova @zacw7