Initial commit: snapshot of spesmilo/electrumx 2.0.0

Unmodified source tree of upstream commit 280cb339aa158e099eb936033eecd15719770651
("Merge pull request #389 from SomberNight/202607_release_2_0",
https://github.com/spesmilo/electrumx, release 2.0.0, 3 July 2026).

All Palladium-specific changes are in the commits that follow.

MANIFEST.in

@@ -0,0 +1,5 @@
+# note: files listed in this file:
+#       - will be added to the sdist
+#       - but won't be added to the wheel (unless by other means)
+
+graft tests/