Now that we construct the TLS client config for cancellation as well as
connect, it feels appropriate to construct the same config once and
re-use it elsewhere. It might also help should #7500 require any extra
setup, so we can easily add it to all the appropriate call sites.
## Problem
While reviewing #10152 I found it tricky to actually determine whether
the connection used `allow_self_signed_compute` or not.
I've tried to remove this setting in the past:
* https://github.com/neondatabase/neon/pull/7884
* https://github.com/neondatabase/neon/pull/7437
* https://github.com/neondatabase/cloud/pull/13702
But each time it seems it is used by e2e tests
## Summary of changes
The `node_info.allow_self_signed_computes` is always initialised to
false, and then sometimes inherits the proxy config value. There's no
need this needs to be in the node_info, so removing it and propagating
it via `TcpMechansim` is simpler.
## Problem
It is called context/ctx everywhere and the Monitoring suffix needlessly
confuses with proper monitoring code.
## Summary of changes
* Rename RequestMonitoring to RequestContext
* Rename RequestMonitoringInner to RequestContextInner
The overall idea of the PR is to rename a few types to make their
purpose more clear, reduce abstraction where not needed, and move types
to to more better suited modules.
