Rebrand hush3 to DragonX and share RandomX dataset across mining threads

Minimal rebrand (see compliant-rebrand branch for full rebrand):
- Rename binaries: hushd/hush-cli/hush-tx → dragonxd/dragonx-cli/dragonx-tx
- Default to DRAGONX chain params without -ac_* flags (randomx, blocktime=36, private=1)
- Update configure.ac: AC_INIT([DragonX],[1.0.0])
- Update client version string and user-agent to /DragonX:1.0.0/
- Add chainparams.cpp with DRAGONX network parameters
- Update build.sh, miner.cpp, pow.cpp for DragonX
- Add bootstrap-dragonx.sh utility script
- Update .gitignore for release directory

Share single RandomX dataset across all mining threads:
- Add RandomXDatasetManager with readers-writer lock, reducing RAM from
  ~2GB per thread to ~2GB total plus ~2MB per thread for the VM scratchpad
- Add LogProcessMemory() diagnostic helper for Linux and Windows

src/hush_bitcoind.h

@@ -403,7 +403,7 @@ int32_t notarizedtxid_height(char *dest,char *txidstr,int32_t *hushnotarized_hei
     params[0] = 0;
     *hushnotarized_heightp = 0;
     if ( strcmp(dest,"HUSH3") == 0 ) {
-        port     = HUSH3_PORT;
+        port     = DRAGONX_PORT;
         userpass = HUSHUSERPASS;
     } else if ( strcmp(dest,"BTC") == 0 )
     {
@@ -498,7 +498,7 @@ int32_t hush_verifynotarization(char *symbol,char *dest,int32_t height,int32_t N
         {
             if ( SMART_CHAIN_SYMBOL[0] != 0 )
             {
-                jsonstr = hush_issuemethod(HUSHUSERPASS,(char *)"getrawtransaction",params,HUSH3_PORT);
+                jsonstr = hush_issuemethod(HUSHUSERPASS,(char *)"getrawtransaction",params,DRAGONX_PORT);
                 //printf("userpass.(%s) got (%s)\n",HUSHUSERPASS,jsonstr);
             }
         }//else jsonstr = _dex_getrawtransaction();