refactor(eth/downloader): drop eth/63

[gzliudan]

Proposed changes

eth/63 predates the XDC-specific protocols and is no longer spoken by any
supported client, so remove it from the advertised capabilities and from
every version-gated branch:

• drop eth63 from ProtocolVersions and protocolLengths, so the node no
  longer advertises the "eth/63" capability
• rename statusData63 to statusData100 and readStatusLegacy to
  readStatus100, xdc/100 now being the only legacy status format
• raise minProtocolVer to 100 and derive errTooOld and the syncWithPeer
  guard from it instead of hardcoding the number in three places
• replace the eth63 version gates in handleMsg and the metered read/write
  wrapper with xdc100
• drop the stale [eth/62] and [eth/63] tags from downloader and queue
  field comments
• stop advertising eth/63 in the devp2p ethtest suite

Tests are renamed to the xdc100/xdc164 constants instead of bare literals
and gain xdc165 coverage where it was missing.

This is a breaking p2p change: peers that only speak eth/63 can no longer
complete the handshake.

Types of changes

What types of changes does your code introduce to XDC network?
Put an ✅ in the boxes that apply

• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Changes that don't change source code or tests
• docs: Documentation only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that neither fixes a bug nor adds a feature
• revert: Revert something
• style: Changes that do not affect the meaning of the code
• test: Adding missing tests or correcting existing tests

Impacted Components

Which parts of the codebase does this PR touch?
Put an ✅ in the boxes that apply

• Consensus
• Account
• Network
• Geth
• Smart Contract
• External components
• Not sure (Please specify below)

Checklist

Put an ✅ in the boxes once you have confirmed below actions (or provide reasons on not doing so) that

• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Tested on a private network from the genesis block and monitored the chain operating correctly for multiple epochs.
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A

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[Copilot]

Pull request overview

Drops legacy eth/63 protocol support across the eth protocol stack and downloader, updating version gating, handshake/status structures, and the test suite to only exercise supported protocol versions.

Changes:

• Removes eth/63 as a supported protocol version and updates version checks to require >= xdc100.
• Renames/updates legacy status packet handling to statusData100 and adjusts handshake/read paths accordingly.
• Updates downloader and eth protocol tests to stop using eth/63 and to align peer/version expectations with the new minimum protocol version.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
eth/sync_test.go	Updates fast-sync disabling tests to use xdc100/xdc165 and runs helper in parallel.
eth/protocol.go	Removes eth/63 constant and updates protocol version/length declarations; renames legacy status packet type.
eth/protocol_test.go	Removes eth/63 status tests and updates status-message error coverage for xdc100.
eth/peer.go	Removes eth/63 handshake paths and switches legacy status handling to xdc100 only.
eth/metrics.go	Updates metrics gating from >= eth63 to >= xdc100.
eth/helper_test.go	Updates test peer handshake to send xdc100 status packet.
eth/handler.go	Updates handler message gating from >= eth63 to >= xdc100.
eth/handler_test.go	Updates handler tests away from eth/63; refactors malformed-block propagation test.
eth/downloader/queue.go	Adjusts peer-id logging and log callsites in header delivery path.
eth/downloader/peer.go	Bumps downloader minimum protocol version to xdc100.
eth/downloader/peer_test.go	Updates peer-set version eligibility tests to exclude eth/63.
eth/downloader/downloader.go	Updates “too old” checks/messages to require >= 100; trims peer IDs in logs.
eth/downloader/downloader_test.go	Updates downloader test matrix from 63/64 to 100/164.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated no new comments.

Suppressed comments (1)

eth/downloader/peer_test.go:29

• TestIdlePeersProtocolVersions is described as covering "every supported" protocol version, but it currently only registers peers for 100 and 164. Since the downloader peer-set supports up to maxProtocolVer=165, this test should include a 165 peer as well (and update the expected totals), otherwise regressions affecting xdc165 eligibility won't be caught.

// TestIdlePeersProtocolVersions verifies that peers running every supported
// protocol version (xdc100, xdc164) are eligible for concurrent
// downloads. A regression here silently disables skeleton filling and body,