explorer: move explorer source code from research to bin/explorer for project releases

This commit relocates the explorer code from the research directory to `bin/explorer` to include it as part of future releases.

### Summary of Updates:

#### Darkfi Project
- Updated `Cargo.toml` to include `bin/explorer/explorerd` as a workspace member
- Updated `Cargo.lock` to include the `explorerd` package
- Updated the `Makefile` to include `explorerd` in the build process

#### Explorer Daemon
- Renamed the project directory from `blockchain-explorer` to `explorer`
- Moved the explorer daemon source code to `bin/explorer/explorerd`
- Updated the cargo package name to `explorerd`
- Updated log statement targets from `blockchain-explorer::` to `explorerd::`
- Renamed the explorer configuration file to `explorerd_config.toml`
- Removed Halo2 patches as they are now included in the root package
- Changed default db_path to use explorerd instead of blockchain-explorer in the path
- Changed binary crate Arg structopt name from blockchain-explorer to explorerd

#### Explorer Site
- Moved the explorer site source code to `bin/explorer/site`
- Updated README.md to include new build instructions for explorerd

bin/explorer/explorerd/Makefile

@@ -0,0 +1,52 @@
+.POSIX:
+
+# Install prefix
+PREFIX = $(HOME)/.cargo
+
+# Cargo binary
+CARGO = cargo +nightly
+
+# Compile target
+RUST_TARGET = $(shell rustc -Vv | grep '^host: ' | cut -d' ' -f2)
+# Uncomment when doing musl static builds
+#RUSTFLAGS = -C target-feature=+crt-static -C link-self-contained=yes
+
+SRC = \
+	Cargo.toml \
+	../../../Cargo.toml \
+	$(shell find src -type f -name '*.rs') \
+	$(shell find ../../../src -type f -name '*.rs') \
+
+BIN = $(shell grep '^name = ' Cargo.toml | sed 1q | cut -d' ' -f3 | tr -d '"')
+
+all: $(BIN)
+
+$(BIN): $(SRC) bundle_contracts_src
+	RUSTFLAGS="$(RUSTFLAGS)" $(CARGO) build --target=$(RUST_TARGET) --release --package $@
+	cp -f ../../../target/$(RUST_TARGET)/release/$@ $@
+	cp -f ../../../target/$(RUST_TARGET)/release/$@ ../../../$@
+
+clean:
+	RUSTFLAGS="$(RUSTFLAGS)" $(CARGO) clean --target=$(RUST_TARGET) --release --package $(BIN)
+	rm -f $(BIN) ../../../$(BIN)
+	rm -rf native_contracts_src
+
+install: all
+	mkdir -p $(DESTDIR)$(PREFIX)/bin
+	cp -f $(BIN) $(DESTDIR)$(PREFIX)/bin
+	chmod 755 $(DESTDIR)$(PREFIX)/bin/$(BIN)
+
+uninstall:
+	rm -f $(DESTDIR)$(PREFIX)/bin/$(BIN)
+
+bundle_contracts_src:
+	@mkdir -p $(CURDIR)/native_contracts_src
+	@(cd ../../../src && \
+		tar -cf $(CURDIR)/native_contracts_src/deployooor_contract_src.tar -C contract/deployooor/src --transform 's,^./,,' . && \
+		tar -cf $(CURDIR)/native_contracts_src/dao_contract_src.tar -C contract/dao/src --transform 's,^./,,' . 2>/dev/null && \
+		find contract/dao/proof -name '*.zk' -exec tar -rf $(CURDIR)/native_contracts_src/dao_contract_src.tar --transform 's,^.*proof/,proof/,' {} + && \
+		tar -cf $(CURDIR)/native_contracts_src/money_contract_src.tar -C contract/money/src --transform 's,^./,,' . && \
+		find contract/money/proof -name '*.zk' -exec tar -rf $(CURDIR)/native_contracts_src/money_contract_src.tar --transform 's,^.*proof/,proof/,' {} + \
+	)
+
+.PHONY: all clean install uninstall bundle_contracts_src