Commit 598e882ee88a1e3 turned `Writer` into a template, and updated most
of the call sites that use it. But not all. The alternative FP printf
system in `float_dec_converter_limited.h` wasn't updated, and neither
was `baremetal/printf.cpp` or `baremetal/vprintf.cpp`.
This patch updates `float_dec_converter_limited.h` in the same way that
the previous commit updated `float_dec_converter.h`: propagate the
templatedness through everything in the header, so that anything using a
`Writer` at all has a `write_mode` template parameter to pass on to it.
`printf.cpp` and `vprintf.cpp` are updated in the same way that the
previous commit updated `printf_core/vfprintf_internal.h`: the
`WriteBuffer` has parameter `WriteMode::FLUSH_TO_STREAM`, and `Writer`
picks it up implicitly from that.
6fea340023