chore: adapt to new SPI module structure

[paullatzelsperger]

What this PR changes/adds

Adapts the Minimum Viable Dataspace to the consolidated EDC SPI module structure. The EDC Connector merges its 40
fine-grained *-spi artifacts into five; this PR remaps the MVD's gradle/libs.versions.toml SPI coordinates onto the
new modules — boot-spi, token-spi, identity-did-spi → core-spi (and consolidates the aliases). The
decentralized-claims-spi, data-plane-signaling-spi and issuerservice-issuance-spi coordinates are unchanged.

Why it does that

The upstream consolidation (eclipse-edc/Connector#5842) removes the individual SPI artifacts MVD depends on; their
content now ships in core-spi. MVD must follow to keep resolving.

Further notes

• Draft: depends on refactor: consolidate SPI modules into five layer-oriented modules eclipse-edc/Connector#5842 being merged and published (and on the corresponding IdentityHub
  adoption, chore: adopt consolidated EDC SPI modules eclipse-edc/IdentityHub#1023). The new artifacts are not on a snapshot repository yet. Verified locally
  against a publishToMavenLocal build of the consolidation + IdentityHub.

Who will sponsor this feature?

TODO: @-mention the sponsoring committer.

Linked Issue(s)

n/a