Add output of VPC subnet tagging to `resourcegroupstaggingapi`

[silv-io]

Motivation

The resourcegroupstaggingapi is lacking support for VPC subnets

Changes

This PR adds VPC subnets to the output of get_resources

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.50%. Comparing base (d8da0ac) to head (2a08924). Report is 4 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8142 +/- ## ======================================= Coverage 94.50% 94.50% ======================================= Files 1150 1150 Lines 99191 99198 +7 ======================================= + Hits 93736 93743 +7 Misses 5455 5455 ``` | [Flag](https://app.codecov.io/gh/getmoto/moto/pull/8142/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto) | Coverage Δ | | |---|---|---| | [servertests](https://app.codecov.io/gh/getmoto/moto/pull/8142/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto) | `28.79% <85.71%> (+<0.01%)` | :arrow_up: | | [unittests](https://app.codecov.io/gh/getmoto/moto/pull/8142/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto) | `94.47% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getmoto#carryforward-flags-in-the-pull-request-comment) to find out more.

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