The thread does not only load blocks, it loads the mempool and,
in a future commit, will start the indexes as well.
Also, renamed the 'ThreadImport' function to 'ImportBlocks'
And the 'm_load_block' class member to 'm_thread_load'.
-BEGIN VERIFY SCRIPT-
sed -i "s/ThreadImport/ImportBlocks/g" $(git grep -l ThreadImport -- ':!/doc/')
sed -i "s/loadblk/initload/g" $(git grep -l loadblk -- ':!/doc/release-notes/')
sed -i "s/m_load_block/m_thread_load/g" $(git grep -l m_load_block)
-END VERIFY SCRIPT-