[build] Move CheckTransaction from lib_server to lib_consensus

CheckTransaction is a context-free function that does not require access
to the blockchain or mempool. Move it from src/consensus/tx_verify in
lib_server to a new unit src/consensus/tx_check in lib_consensus so that
it can be called by non-server libraries.

src/Makefile.am

@@ -124,6 +124,7 @@ BITCOIN_CORE_H = \
   compat/sanity.h \
   compressor.h \
   consensus/consensus.h \
+  consensus/tx_check.h \
   consensus/tx_verify.h \
   core_io.h \
   core_memusage.h \
@@ -391,6 +392,7 @@ libbitcoin_consensus_a_SOURCES = \
   consensus/merkle.cpp \
   consensus/merkle.h \
   consensus/params.h \
+  consensus/tx_check.cpp \
   consensus/validation.h \
   hash.cpp \
   hash.h \