x.json2.decoder2: use Linked List data structure strategy

[enghitalo]

changes

• Improve performance between 50% and 200%
• Replace array and node to only LinkedList
• decode string
• decode map
• decode array
• decode time

Benchmarks

 ./v wipe-cache && ./v -prod -cc gcc crun vlib/x/json2/decoder2/tests/bench.v 
 
V cache folder /home/hitalo/.vmodules/.cache was wiped.
V tmp.c and tests folder folder /tmp/v_1000 was wiped.
Starting benchmark...
max_iterations: 1000000

***Structure and maps***
 SPENT   349.628 ms in decoder2.decode[Stru](json_data)!
 SPENT   369.915 ms in old_json.decode(Stru, json_data)!

 SPENT    99.198 ms in decoder2.decode[StructType[string]](json_data1)!
 SPENT    92.955 ms in old_json.decode(StructType[string], json_data1)!

 SPENT   121.837 ms in decoder2.decode[StructTypeOption[string]](json_data1)!
 SPENT   143.498 ms in old_json.decode(StructTypeOption[string], json_data1)!

 SPENT    64.695 ms in decoder2.decode[StructType[int]](json_data2)!
 SPENT    88.690 ms in old_json.decode(StructType[int], json_data2)!

 SPENT   209.812 ms in decoder2.decode[map[string]string](json_data1)!
 SPENT   183.958 ms in old_json.decode(map[string]string, json_data1)!


***arrays***
 SPENT   313.657 ms in decoder2.decode[[]int]('[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]')!
 SPENT   551.574 ms in old_json.decode([]int, '[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]')!


***simple types***
 SPENT    20.992 ms in decoder2.decode[int]('2')!
 SPENT    19.372 ms in decoder2.decode[bool]('true')!
 SPENT   738.004 ms in decoder2.decode[time.Time]('2022-03-11T13:54:25')!
 SPENT    90.998 ms in decoder2.decode[string]('"abcdefghijklimnopqrstuv"')!

[spytheman]

Please solve the conflict, by rebasing on master or merging.

[spytheman]

Thank you.

[spytheman]

remove this comment, it is useless

[spytheman]

Use a string builder, not a private implementation of it, that will be harder to understand in the future.

[enghitalo]

I think buffer less complex than strings builder and not needs import strings

[spytheman]

Good work.