Fix spelling errors

Most errors found with:

codespell -L cach,thst,odly,aslo,parm,parms,inpu,ges,prset,pevent,ptd,pring,valu,noo,noe,ned,inout,ro,siz,froms,nd,fo,singl,sart,multy,tthe,allong,ment,inate,nodel,tring,alse,ture,thi,wille,numer

Some more manually found (its -> it's)

c++20: Do not use apostrophe (e.g. can't) in unquoted #error message

modules/libcom/test/epicsAtomicTest.cpp

@@ -360,7 +360,7 @@ void testBasic()
     using epics::atomic::subtract;
     using epics::atomic::compareAndSwap;
 
-    testDiag("Test basic operation symantics");
+    testDiag("Test basic operation semantics");
 
     int Int = 0;
     size_t Sizet = 0;