e2e: Allow disabling PEX reactor

[lasarojc]

Feature Request

During experimentation it may be useful to disable peer discovery on the whole setup and only connect to peers specified in the config.toml

Summary

Allow disabling the PEX reactor in the manifests.

Problem Definition

When experimenting, restarting leads to a different overlay network being set every time, casting doubt on comparison results.

Proposal

Allow disabling the PEX on manifests so that connections are only stablished to the peers specified in generated config.toml

[cason]

Please refer that this applies to end-to-end tests or qa-infrastructure.

We can disable PEX on regular nodes, there is a configuration key for that: https://github.com/cometbft/cometbft/blob/main/config/toml.go#L360

[lasarojc]

Please refer that this applies to end-to-end tests or qa-infrastructure.

We can disable PEX on regular nodes, there is a configuration key for that: https://github.com/cometbft/cometbft/blob/main/config/toml.go#L360

Updated to reflect the limitation on specifying the flag on manifests, not individual configs.