feat(cage): depend on pure cardano-tx-tools:tx-build sublibrary
cardano-mpfs-cage's library and e2e-test use only the pure
Cardano.Tx.{Build,Balance,Ledger} surface, which now lives in the
cross-target `cardano-tx-tools:tx-build` sub-library. Depend on it
directly instead of the full cardano-tx-tools library, so the cage
package's transaction-building closure is free of the node/IO surface
(http-client-tls, haskeline, chain-follower, …).
Bump the cardano-tx-tools pin to 631f1341 (where tx-build is exposed)
and set -build-node-tools so the solver does not pull tx-tools' node
components (which require ouroboros 3.x, conflicting with this project's
ouroboros-consensus ==1.0.0.0 pin).
Enables the MPFS cage-helper wasm cross-target build
(cardano-mpfs-offchain#258).