protogen(xml): improve XML importer v2.1

[Kybxd]

1. add support for scalar/enum list and predefined struct list

   
   <?xml version="1.0" encoding="UTF-8"?>
   <!--
   <@TABLEAU>
   <Item Sheet="ItemConf" />
   </@TABLEAU>

[int32] [enum<.FruitType>]

-->

1 FRUIT_TYPE_APPLE FRUIT_TYPE_ORANGE FRUIT_TYPE_BANANA

2. for all kinds of lists and maps, auto add the `list` or `map` suffix on generated field name, so you don't need to manually add the  `list` or `map` suffix, or use plurals when naming a xml node or attribute

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 86.66667% with 10 lines in your changes missing coverage. Please review.

Project coverage is 55.29%. Comparing base (4aca14f) to head (a94df7c). Report is 1 commits behind head on master.

Files	Patch %	Lines
internal/importer/xml.go	86.11%	8 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #132 +/- ## ========================================== + Coverage 55.13% 55.29% +0.16% ========================================== Files 74 74 Lines 9185 9241 +56 ========================================== + Hits 5064 5110 +46 - Misses 3566 3574 +8 - Partials 555 557 +2 ```

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