Migrate remaining exits to FATAL_*_ERROR calls (#704)

Adds FATAL for things that are most likely programming errors in executable_semantics.

executable_semantics/testdata/experimental_continuation9.golden

@@ -1,2 +1,2 @@
-RUNTIME ERROR: 12: : undefined behavior: access to dead value 1
+RUNTIME ERROR: 12: undefined behavior: access to dead value 1
 EXIT CODE: 255

executable_semantics/testdata/fun_named_params2.golden

@@ -1,2 +1,2 @@
-ERROR: 5: positional members must come before named members
+PROGRAM ERROR: 5: positional members must come before named members
 EXIT CODE: 255

executable_semantics/testdata/generic_function_fail2.golden

@@ -1,2 +1,2 @@
-10: error, could not deduce type argument for type parameter T
+COMPILATION ERROR: 10: could not deduce type argument for type parameter T
 EXIT CODE: 255

executable_semantics/testdata/global_variable8.golden

@@ -1,2 +1,2 @@
-RUNTIME ERROR: 8: : could not find `y`
+RUNTIME ERROR: 8: could not find `y`
 EXIT CODE: 255

executable_semantics/testdata/invalid_char.golden

@@ -1,2 +1,2 @@
-1.1: invalid character '\xFE' in source file.
-EXIT CODE: 1
+COMPILATION ERROR: 1: invalid character '\xFE' in source file.
+EXIT CODE: 255

executable_semantics/testdata/pattern_variable_fail.golden

@@ -1,2 +1,2 @@
-executable_semantics/testdata/pattern_variable_fail.carbon:7: syntax error, unexpected :
+COMPILATION ERROR: 7: syntax error, unexpected :
 EXIT CODE: 255

executable_semantics/testdata/tuple4.golden

@@ -1,2 +1,2 @@
-ERROR: 6: positional members must come before named members
+PROGRAM ERROR: 6: positional members must come before named members
 EXIT CODE: 255