Port `bridge` network documentation to `gendoc`

[stgraber]

The bridge network documentation (doc/reference/network_bridge.md) currently uses a static table of valid options. This should be moved to an auto-generated table using gendoc.

This is typically done in two steps:

1. Add the required gendoc comments where the configuration options are defined (usually alongside their validator)
2. Generate the new config metadata (make update-metadata)
3. Update the documentation to use the generated metadata

See #847 for an example.

[NathanChase22]

Hey @stgraber , I'm a UT student having to contribute to an open source project for Professor Chidambaram's Virtualization course.

[stgraber]

Done!

[NathanChase22]

This is the results from my last run of spell checker. These words were found in the official bridge documentation, so I am unsure what the issue is here

Misspelled words:
doc/html/reference/network_bridge/index.html: html>body>div>div>div>div>article>section>section>div>div>span>p

openvswitch

Misspelled words:
doc/html/reference/network_bridge/index.html: html>body>div>div>div>div>article>section>section>div>div>span>p

dns

Misspelled words:
doc/html/reference/network_bridge/index.html: html>body>div>div>div>div>article>section>section>div>div>span>p

vxlan

[stgraber]

You should keep the PR open, you can still push changes to it while it's open and it makes it easier for us to suggest tweaks and changes.

Those kind of misspell triggers are very usual. In some cases they're just wrong and we'll add the word to the wordlist while in other cases we just need to escape the word in question or capitalize it to have it be compliant with the doc checker.