refactor: consolidate SPI modules into five layer-oriented modules

[paullatzelsperger]

What this PR changes/adds

Implements the decision record
2026-06-18-spi-module-consolidation:
the 45 fine-grained modules under spi/ are merged into five coarse, layer-oriented modules, and the layout is
flattened to spi/<name>-spi:

New module	Absorbs
core-spi	boot, http, web, json-ld, transform, validator, transaction(+datasource), policy-model, token, jwt, keys, encryption, oauth2, auth, identity-did, verifiable-credentials, connector-participant-context, vault-hashicorp, data-address-*
control-plane-spi	asset, catalog, contract, transfer, policy, secrets, policy-engine, participant, request-policy-context, cel, participant-context-single/config, edr-store, task, policy-monitor, data-plane-selector, federated-catalog, crawler
data-plane-spi	data-plane-http-spi
dcp-spi	renamed from decentralized-claims-spi
dataspace-protocol-spi	renamed from protocol-spi

All ~257 consumer build.gradle.kts, the dist/bom/ BOMs and settings.gradle.kts are rewritten to the new paths.

Why it does that

implements the D-R

Further notes

• Breaking change for downstream adopters: 40 published Maven coordinates (org.eclipse.edc:boot-spi,
  :transfer-spi, :asset-spi, …) disappear; their content now ships in one of the five modules above. The five new
  artifactIds are core-spi, control-plane-spi, data-plane-spi, dcp-spi, dataspace-protocol-spi.
• Surplus @Spi package-info annotations are reduced to one per merged module (autodoc requires a single SPI
  definition per module); the package javadoc is preserved.
• Fixes a latent unfinished Mockito verify() in AbstractJsonLdTransformerReturnObjectTest that only surfaced once
  the transform-spi tests joined core-spi's test task.
• All source moves use git mv to preserve history.
• The DR's layering diagram is updated to match the final mapping (federated-catalog folded into control-plane-spi;
  dcp-spi → control-plane-spi edge).

Who will sponsor this feature?

TODO: @-mention the sponsoring committer.

Linked Issue(s)

n/a — tracked via the decision record.

[ndr-brt]

[ndr-brt]

on trust