Add all root project env files to ImportantFiles

[haidubogdan]

Closes #9229

• add all root project env files to ImportantFiles
• additional coloring lexer fix for single quoted string with slash
• remove envFileResolver service and replace it with a mime-resolver.xml to handle mime file association
• all files containing .env. in their name are associated with text/x-env mimetype

Coloring fix for single quoted string

There was a escape done on slash inside strings, which created a small coloring issue.

Before:

After:

File association

Before:
.env.test and .env.local.demo were not under env mime type

After:

---

^Add meaningful description above

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