Add documentation for DenonAVR telnet feature

[dcmeglio]

Proposed change

Adds a couple more supported AVRs to the list (based on my personal testing), fixed some mistakes related to zone 1/zone 2 really should be zone 2/zone 3, added documentation for new telnet feature.

Type of change

• Spelling, grammar or other readability improvements (current branch).
• Adjusted missing or incorrect information in the current documentation (current branch).
• Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • I've opened up a PR to add logo's and icons in Brands repository.
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase: Add support for telnet connections for Denonavr integration core#85980
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: fixes #

Checklist

• This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• The documentation follows the Home Assistant documentation standards.

[frenck]

✅ Approved. Can be merged as soon as the parent PR gets merged.

[dcmeglio]

@frenck per some PR reviews on the parent, I've changed the default value of use_telnet to true. To prevent a breaking change though it will remain false for existing installs but will be true if you setup a new install. I added text to hopefully make this clear but let me know if there is a better way.