Changed file names

Changed stdlib_bitset_64.fypp and stdlib_bitset_large.fypp to
stdlib_bitsets_64.fypp and stdlib_bitsets_large.fypp.

[ticket: X]

Author: wclodius2

src/stdlib_bitset_64.fypp renamed to src/stdlib_bitsets_64.fypp

@@ -1,5 +1,5 @@
 #:include "common.fypp"
-submodule(stdlib_bitsets) stdlib_bitset_64
+submodule(stdlib_bitsets) stdlib_bitsets_64
     implicit none
 
 contains
@@ -1140,4 +1140,4 @@ contains
     end subroutine xor_64
 
 
-end submodule stdlib_bitset_64
+end submodule stdlib_bitsets_64

src/stdlib_bitset_large.fypp renamed to src/stdlib_bitsets_large.fypp

@@ -1,5 +1,5 @@
 #:include "common.fypp"
-submodule(stdlib_bitsets) stdlib_bitset_large
+submodule(stdlib_bitsets) stdlib_bitsets_large
     implicit none
 
 contains
@@ -1367,4 +1367,4 @@ contains
 
     end subroutine xor_large
 
-end submodule stdlib_bitset_large
+end submodule stdlib_bitsets_large