feat(sdk): rename attribute to #[chain_module], keep #[fai_module] alias

The public macro name was the last product-scoped 'fai' identifier
in the SDK surface. #[chain_module] is now the primary attribute
(README + examples updated); #[fai_module] stays as a delegating
alias so modules written before the rename keep compiling. 0.2.1.

Signed-off-by: flemming-it <sf@flemming.it>

examples/echo/Cargo.lock

@@ -34,7 +34,7 @@ checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
 [[package]]
 name = "chain-module-sdk"
-version = "0.1.2"
+version = "0.2.0"
 dependencies = [
  "chain-module-sdk-macros",
  "serde",
@@ -45,7 +45,7 @@ dependencies = [
 
 [[package]]
 name = "chain-module-sdk-macros"
-version = "0.1.2"
+version = "0.2.0"
 dependencies = [
  "proc-macro2",
  "quote",