Scala3: test against both LTS & Next, build with LTS

[bjaglin]

Rationale

• test against LTS & Next -> test the 2 Scala3 versions we can expect in the wild
• build with LTS -> prepare for Publish cli_3 & rules_3, built against core_2.13 #1680

 sbt:scalafix> projects
 [info] In file:/home/brice/git/scala/scalafix/
 [info] 	   cli2_12
 [info] 	   cli2_13
 [info] 	   cli3
 [info] 	   core2_12
 [info] 	   core2_13
 [info] 	   core3
 [info] 	   docs2_13
 [info] 	   expect2_12Target2_12_18
 [info] 	   expect2_12Target2_12_19
 [info] 	   expect2_12Target2_12_19xsource3
 [info] 	   expect2_13Target2_13_12
 [info] 	   expect2_13Target2_13_13
 [info] 	   expect2_13Target2_13_14
 [info] 	   expect2_13Target2_13_14xsource3
+[info] 	   expect2_13Target3_3_4-RC1
 [info] 	   expect2_13Target3_4_2
-[info] 	   expect3Target3_4_2
+[info] 	   expect3Target3_3_4-RC1
 [info] 	   input2_12_18
 [info] 	   input2_12_19
 [info] 	   input2_12_19xsource3
 [info] 	   input2_13_12
 [info] 	   input2_13_13
 [info] 	   input2_13_14
 [info] 	   input2_13_14xsource3
+[info] 	   input3_3_4_RC1
 [info] 	   input3_4_2
 [info] 	   integration2_12
 [info] 	   integration2_13
 [info] 	   integration3
 [info] 	   interfaces
 [info] 	   output2_12_19
 [info] 	   output2_12_19xsource3
 [info] 	   output2_13_14
 [info] 	   output2_13_14xsource3
-[info] 	   output3_4_2
+[info] 	   output3_3_4_RC1
 [info] 	   reflect2_12
 [info] 	   reflect2_13
 [info] 	   reflect3
 [info] 	   rules2_12
 [info] 	   rules2_13
 [info] 	   rules3
 [info] 	 * scalafix
 [info] 	   shared2_12
 [info] 	   shared2_13
 [info] 	   shared3
 [info] 	   testkit2_12
 [info] 	   testkit2_13
 [info] 	   testkit3
 [info] 	   unit2_12
 [info] 	   unit2_13
 [info] 	   unit3