feat: clean up `p2p` & implement bootnode (`seed` peers) support

[zivkovicmilos]

Description

This PR introduces bootnode (seed mode) support for TM2 peering, and cleans up parts of the p2p module codebase.

Closes #2308

Contributors' checklist...

• [x] Added new tests, or not needed, or not feasible
• [x] Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• [x] Updated the official documentation or not needed
• [x] No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• [x] Added references to related issues and PRs
• [ ] Provided any useful hints for running manual tests
• [ ] Added new benchmarks to generated graphs, if any. More info here.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 81.44215% with 332 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
tm2/pkg/p2p/switch.go	74.87%	91 Missing and 7 partials :warning:
tm2/pkg/p2p/mock/peer.go	55.85%	80 Missing and 3 partials :warning:
tm2/pkg/p2p/discovery/discovery.go	80.71%	20 Missing and 7 partials :warning:
tm2/pkg/bft/node/node.go	81.66%	15 Missing and 7 partials :warning:
tm2/pkg/p2p/transport.go	89.72%	13 Missing and 6 partials :warning:
tm2/pkg/p2p/types/key.go	66.07%	14 Missing and 5 partials :warning:
tm2/pkg/internal/p2p/p2p.go	89.75%	17 Missing :warning:
tm2/pkg/p2p/types/netaddress.go	84.94%	11 Missing and 3 partials :warning:
tm2/pkg/bft/rpc/core/net.go	0.00%	7 Missing :warning:
tm2/pkg/bft/blockchain/reactor.go	66.66%	5 Missing :warning:
... and 9 more

:loudspeaker: Thoughts on this report? Let us know!

[zivkovicmilos]

There is a leftover issue with this PR that I'm currently investigating, which is a hanging test somewhere in TM2.

I will resolve this before opening the PR for reviews 🙏

[zivkovicmilos]

Opening this up for an initial review 🙏

I have no idea why the gno.land testing suite hangs on the PR -- it runs fine locally 🤷‍♂️

[zivkovicmilos]

@sw360cab @albttx @r3v4s

Ready for you to take this for a spin 🙏

[Gno2D2]

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