bpf: suppress false-positive clang-tidy/clangd diagnostics under src/bpf

clang-tidy's misc-use-internal-linkage fires on BPF map declarations
(they have the SEC(".maps") attribute and must retain external linkage
so bpftool gen skeleton can resolve them as ELF symbols), and its
misc-include-cleaner flags errno.h as unused even where a /* IWYU
pragma: keep */ is present. clangd's own unused-includes analysis
emits the equivalent diagnostic independently of clang-tidy.

Add src/bpf/.clang-tidy and src/bpf/.clangd that inherit the parent
configs and scope these suppressions to BPF sources only.

src/bpf/.clang-tidy

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+---
+InheritParentConfig: true
+Checks: '-misc-use-internal-linkage'
+CheckOptions:
+  misc-include-cleaner.IgnoreHeaders: 'errno\.h'
+...

src/bpf/.clangd

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+Diagnostics:
+  Includes:
+    IgnoreHeader: [errno\.h]