[loki] Json|Logfmt Parser returns empty label value if it contains symbol `�`

[vlad-diachenko]

Describe the bug

When the Logfmt or JSON parser meets the symbol � inside the label value, it skips the whole label or replaces the value with an empty string.

Loki drops the value(here and here) because PromQL engine fails the query if it meets such symbols.

To Reproduce Open LogQL analyzer page and run the query:

1. Logfmt example

2. JSON example

Expected behavior Label value must be replaced with (symbol: space) instead of dropping the label or label value.

Environment:

• Infrastructure: any
• Deployment tool: any