[gdb/testsuite] Fix read1 timeout in gdb.base/info-types-c++.exp

[gdb/testsuite] Fix read1 timeout in gdb.base/info-types-c++.exp

When running test-case gdb.base/info-types-c++.exp with check-read1 I run
into:
...
425:    typedef const void * std::allocator_traits<std::allocator<std::\
  _Sp_counted_ptr_inplace<std::filesystem::__cxx11::\
  recursive_directory_iterator::_Dir_stack, std::allocator<std::filesystem::\
  __cxx11::recursive_directory_iterator::_Dir_stack>, \
  FAIL: gdb.base/info-types-c++.exp: info types (timeout)
...

The corresponding gdb_test_multiple does contain an exp_continue which
resets the timeout counter every time info for another file is printed, but
this doesn't help for this timeout because it times out during printing info
for a single file.

Fix this by processing line-by-line.

Tested on x86_64-linux, both with gcc-7.5.0 and gcc-4.8.5 (the latter is
different because the "unsigned int" type is missing).

gdb/testsuite/ChangeLog:

2021-05-19  Tom de Vries  <tdevries@suse.de>

	* gdb.base/info-types.exp.tcl: Scan info types output line-by-line.