sandbox/linux/bpf_dsl: add DumpBPF::StringPrintProgram
Android doesn't have open_memstream, so the code had to be cleaned up
to use something else. base::StringAppendF seems like the least bad
option, and this code will eventually be test-only code anyway.
While here, clean up the code to be clang-format'able. Also, satisfy
my pedantic side by switching from int casts to using <inttypes.h>.
BUG=414363
Review URL: https://codereview.chromium.org/
1310683002
Cr-Commit-Position: refs/heads/master@{#345195}