luci-mod-network: DHCP tabs redesign phase 2

[systemcrash]

This is a continuation of the work done in #6705. It implements GUI for dnsmasq based tags. Tags can trigger DHCP options (to be sent in DHCP responses), and vice-versa: DHCP client options and properties e.g. MAC/Vendor/User Class can trigger creation of tags. Recommended for users who know what they are doing, since invalid option:value combos can crash dnsmasq.

To describe tags succinctly is a challenge, such that a newcomer understands them more deeply, since they operate in two domains: ingress and egress. I spent a while coming up with the current descriptions. Suggestions welcome, but modifier beware. Syntax and descriptions are terse since you are expected to know what options and values you need.

Note: tags are still called 'networkid' in the dnsmasq.init script, which is really old terminology and should be updated. Current dnsmasq manpage and docu details 'tags' as the current terminology with little more than a footnote mentioning networkid any more.

• [x] This PR is not from my main or master branch :poop:, but a separate branch :white_check_mark:
• [x] Each commit has a valid :black_nib: Signed-off-by: <[email protected]> row (via git commit --signoff)
• [x] Each commit and PR title has a valid :memo: <package name>: title first line subject for packages
• [x] Tested on: 23.05.3
• [x] ( Preferred ) Screenshot or mp4 of changes:
• [x] Description: (describe the changes proposed in this PR)

https://github.com/openwrt/luci/assets/647633/d939de2a-e577-4d41-b764-3aa74cb894b8

[systemcrash]

Thanks for the ideas @feckert. Tags are difficult...

[miyatsu]

What is the status of this PR?

[edrikk]

This looks good and I do agree that it's a very useful thing to be able to control via UI vs. manual config file updates.