Remove Gloo Edge references

[PetrMc]

Description

Replaced most of the references to Gloo Edge with kgateway across the codebase.

API changes

None

Code changes

no code changes. Mostly text, some of comments and formatting.

CI changes

None

Docs changes

Updated some text in READMEs

Context

This is part of the ongoing effort to align terminology with kgateway.

Interesting decisions

none :-)

Testing steps

not required. Just search to return any references:

grep -r -i "gloo edge" --exclude-dir=".git" ../kgateway | wc -l

Notes for reviewers

No functional changes—this is a purely textual update. Original discussion is Slack

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works