Log latency stats and remove old unused latency mechanism

[Tyriar]

Fixes #187274

This change measures latency in an idle callback after each terminal process is created.

Example logs:

2023-07-07 08:38:15.407 [info] Latency measurements for test+test backend
window<->ptyhostservice<->ptyhost: 16.70ms
ptyhostservice<->ptyhost: 0.75ms []

2023-07-07 08:38:44.243 [info] Latency measurements for local backend
window<->ptyhost (message port): 0.40ms
window<->ptyhostservice<->ptyhost: 1.30ms
ptyhostservice<->ptyhost: 0.45ms []

[meganrogge]

should this label include remote?

[meganrogge]

oh nvm looks like that happens https://github.com/microsoft/vscode/pull/187281/files#diff-38cb820e08ef9a8479ff998378fa4b33cd3a9e57461329ded57f8a4b5e8dae4aR396