[gdb/testsuite] Simplify gdb.base/sect-cmd.exp

While looking at gdb.base/sect-cmd.exp, I noticed a few things that can be
simplified:
- use gdb_test instead of gdb_test_multiple
- use -wrap "" as regexp

Also, I noticed this:
...
           fail "$gdb_test_name, saw not found marker"
...
while our usual test naming scheme uses parentheses, like so:
...
           fail "$gdb_test_name (saw not found marker)"
...

Fix the test-name and do the simplifications.

Tested on x86_64-linux.

gdb/testsuite/ChangeLog:

2021-06-08  Tom de Vries  <tdevries@suse.de>

	* gdb.base/sect-cmd.exp: Use gdb_test.  Use -wrap "".  Fix
	test name.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2021-06-08  Tom de Vries  <tdevries@suse.de>
+
+	* gdb.base/sect-cmd.exp: Use gdb_test.  Use -wrap "".  Fix
+	test name.
+
 2021-06-08  Tom de Vries  <tdevries@suse.de>
 
 	* gdb.base/sect-cmd.exp: Fix saw_section_address_line regexp.

gdb/testsuite/gdb.base/sect-cmd.exp

@@ -63,21 +63,17 @@ gdb_test_multiple "section $section_name $address1" \
 	    exp_continue
 	}
 	-re "Section \[^\r\n\]+ not found\r\n" {
-	    fail "$gdb_test_name, saw not found marker"
+	    fail "$gdb_test_name (saw not found marker)"
 	    exp_continue
 	}
-	-re "$gdb_prompt $" {
+	-re -wrap "" {
 	    gdb_assert { $saw_section_address_line } $gdb_test_name
 	}
     }
 
 # Verify that GDB responds gracefully to a non-existent section name.
 #
-gdb_test_multiple "section FOOBARBAZ 0x1234" "" {
-    -re -wrap "Section FOOBARBAZ not found" {
-	pass $gdb_test_name
-    }
-}
+gdb_test "section FOOBARBAZ 0x1234" "Section FOOBARBAZ not found"
 
 # Check that GDB can still print the error message when the section
 # name is very long.  It used to be the case that GDB could only print
@@ -86,9 +82,6 @@ gdb_test_multiple "section FOOBARBAZ 0x1234" "" {
 #
 set long_sect_name \
     "A234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123"
-gdb_test_multiple "section $long_sect_name 0x1234" \
-    "non-existent too-long section disallowed" {
-	-re -wrap "Section $long_sect_name not found" {
-	    pass $gdb_test_name
-	}
-    }
+gdb_test "section $long_sect_name 0x1234" \
+    "Section $long_sect_name not found" \
+    "non-existent too-long section disallowed"