[stable] Backports (#8782)

* Fix light sync with initial validator-set contract (#8528)

* Fix #8468

* Use U256::max_value() instead

* Fix again

* Also change initial transaction gas

* Don't open Browser post-install on Mac (#8641)

Since we start parity with the UI disabled per default now, opening the browser post installation will show an annoying error message, confusing the user. This patch removes opening the browser to prevent that annoyance.

fixes #8194

* Prefix uint fmt with `0x` with alternate flag

* Set the request index to that of the current request (#8683)

* Set the request index to that of the current request

When setting up the chain of (two) requests to look up a block by hash, the second need to refer to the first. This fixes an issue where the back ref was set to the subsequent request, not the current one. When the requests are executed we loop through them in order and ensure the requests that should produce headers all match up. We do this by index so they better be right.

In other words: off by one.

* Node table sorting according to last contact data (#8541)

* network-devp2p: sort nodes in node table using last contact data

* network-devp2p: rename node contact types in node table json output

* network-devp2p: fix node table tests

* network-devp2p: note node failure when failed to establish connection

* network-devp2p: handle UselessPeer error

* network-devp2p: note failure when marking node as useless

* network-devp2p: handle UselessPeer disconnect (#8686)