Ytt removes quotes for hex strings, which makes them ambiguous

**What steps did you take:**

```shell
echo 'hex-string: "0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed"' > template.yaml
ytt -f template.yaml
```

**What happened:**

quotes removed

**What did you expect:**

quotes preserved, as hex string format might contain specific encoding where string format required (e.g. upper/lower case letters provides checksum)

**Environment:**

- ytt version (use `ytt --version`): 0.45.0
- OS (e.g. from `/etc/os-release`): Fedora 36

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