XDRIVE transport: Support XMUX ("maxConnections": 4 on Google Drive by default) and h3

[4RH1T3CT0R7]

as RPRX asked in #7181. xmux the way masque has it, maxConnections 4 on google drive over h2 and 1 otherwise by default: a session takes a connection of xmux and moves to another after hMaxRequestTimes or hMaxReusableSecs, and the old one closes once its requests end. and h3 with alpn ["h3"] like DoH: quicParams and udp masks from finalmask, chrome parrot, bbr by default like xhttp, no fallback to h2 for now, with google-drive only noise among the udp masks

from a VPS to googleapis with 150 ms added, 32 parallel 4 MiB puts: google gives an h2 connection 1 MiB of window, so on one connection they make 3.4 MiB/s, spread over 4 connections 9-11, and one h3 connection makes 16.5, so h3 takes one by default

[RPRX]

似乎需要 rebase

[RPRX]

感觉这个 PR 最好配合 #7135 ，虽然我不确定 TSPU 会不会针对 Google IP 也限制旧版 Chrome 指纹的连接数

所以 h3 时默认 maxConnections 是 1？

[4RH1T3CT0R7]

@RPRX rebased. it was 4 with h3 as well, now h3 takes 1 by default and the 4 stays for h2, one h3 connection made 16.5 MiB/s where four on h2 made 9-11. xdrive takes the chrome fingerprint by default, so #7135 moves it to chrome 155 with nothing to change here