Add mediator and simple client implementation #6275

Job	Run time
aries_vcx_clippy (credx,vdrtools_wallet)	2m 1s
aries_vcx_no_features_clippy	2m 2s
aries_vcx_clippy (vdr_proxy_ledger)	2m 2s
verify-code-formatting	21s
workflow-setup	34s
workspace_clippy	2m 2s
aries_vcx_core_clippy (credx,vdrtools_wallet)	1m 58s
aries_vcx_core_clippy (vdr_proxy_ledger)	2m 2s
test-unit-workspace	1m 22s
test-integration-aries-vcx	1m 19s
code-coverage-aries-vcx-integration-modular-libs	1m 18s
build-docker-vdrproxy	1m 20s
workflow-setup-check	1s
test-integration-aries-vcx-mysql	1m 15s
test-integration-did-crate	1m 18s
test-integration-libvcx	1m 13s
test-integration-node-wrapper (18.x)	1m 12s
x86_64-unknown-linux-gnu	1m 19s
x86_64-unknown-linux-musl	1m 5s
x86_64-apple-darwin	1m 12s
aarch64-apple-darwin	1s
test-integration-aries-vcx-vdrproxy	1s
publish-docker-vdrproxy	1s
publish-napi	1s
make-release	1s
publish-node-wrapper	1s
publish-agent-core	1s
	27m 3s

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