Sync with upstream java-tron 4.8.2 protos (GreatVoyage-v4.8.2.1)

[maoueh]

Syncs this fork with upstream tronprotocol/protocol at 8432beca ("Merge pull request tronprotocol#256 from halibobo1205/release_4.8.2"), so it carries the protos shipped with java-tron GreatVoyage-v4.8.2.1.

GreatVoyage-v4.8.2.1 is a dependency-bump release (libp2p 2.2.8 -> 2.2.9, grpc-java 1.81.0 -> 1.83.0) plus HTTP API performance work. It contains no proto change of its own, and upstream has no 4.8.2.1 sync commit — its HEAD is still the 4.8.2 merge. So syncing to 8432beca is what "support 4.8.2.1" means at the proto level.

Previous sync point was upstream 4c726956 (java-tron 4.8.1).

Upstream changes in this range

• api/api.proto: all option (google.api.http) = {...} grpc-gateway annotations removed from the service definitions, and the import "google/api/annotations.proto"; line dropped. This is the "improve HTTP API performance" item.
• api/api.proto: IvkDecryptTRC20Parameters.events and OvkDecryptTRC20Parameters.events marked [deprecated = true]; shiededTransaction comment typo fixed.
• core/Tron.proto, core/Discover.proto: a single blank line removed each.
• core/tron/*.proto: 8 empty placeholder files deleted upstream. This fork had already removed them, so nothing to do.
• Both protocol documentation files refreshed.

Verified: the RPC list is byte-for-byte identical between 4c726956 and 8432beca, and no message, field or enum definition changed. This is wire-compatible.

Changes in this PR

1. Merge of upstream 8432beca. Merged cleanly — no conflicts. All StreamingFast deltas are preserved: the go_package rewrites, core/contract/*.proto flattened into core/, the pb/ bindings, buf.* config and .github/ workflows.
2. buf.build/googleapis/googleapis removed from buf.yaml and buf.lock, since no proto imports google/api/annotations.proto any more. google.golang.org/genproto/googleapis/api correspondingly dropped from go.mod.
3. pb/api regenerated with buf generate. pb/core is unchanged.
4. README: dropped the now-stale "Removed empty core/tron/*.proto files" bullet — upstream removed them too, so it is no longer a divergence.

Impact on the generated Go API

The exported surface is identical — same types, same methods, same gRPC client/server interfaces. Diffing exported type/func declarations before and after regeneration produces no output for both api.pb.go and api_grpc.pb.go.

What actually changed in pb/api:

• the embedded file descriptor bytes, reflecting the removed HTTP annotations;
• doc comments (the shieldedTransaction typo fix);
• // Deprecated: markers on IvkDecryptTRC20Parameters.GetEvents() and OvkDecryptTRC20Parameters.GetEvents();
• protoc-gen-go-grpc version comment v1.6.1 -> v1.6.2.

Nothing here breaks firehose-tron, which imports pb/api and pb/core.

Verification

• buf build — OK
• go build ./... — OK
• go test ./... — OK
• go vet ./... — OK
• buf generate is idempotent on the committed tree, and go mod tidy is a no-op.

Follow-ups after merge (not done here)

• Tag the merge commit. Note .github/workflows/buf.yml only triggers on tags: v*, so a GreatVoyage-v4.8.2.1 tag alone will not publish to the BSR — the plain v4.8.2.1 tag is the one that runs buf push --label=main.
• No CHANGELOG.md was added: this repo has never had one and uses release tags to map fork versions to java-tron versions.