perf header: Add sanity checks to HEADER_BPF_BTF processing

perf header: Add sanity checks to HEADER_BPF_BTF processing

Validate the BTF entry count and individual data sizes when reading
HEADER_BPF_BTF from perf.data files to prevent excessive memory
allocation from malformed files.

Reuses the MAX_BPF_PROGS (131072) and MAX_BPF_DATA_LEN (256 MB)
limits from HEADER_BPF_PROG_INFO processing.

Cc: Song Liu <song@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Assisted-by: Claude Code:claude-opus-4-6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>