kernel: Add chainstate manager object to C header

This is the main driver class for anything validation related, so expose
it here.

Creating the chainstate manager options will currently also trigger the
creation of their respectively configured directories.

The chainstate manager and block manager options are consolidated into a
single object. The kernel might eventually introduce a separate block
manager object for the purposes of being a light-weight block store
reader.

The chainstate manager will associate with the context with which it was
created for the duration of its lifetime and it keeps it in memory with
a shared pointer.

The tests now also create dedicated temporary directories. This is
similar to the behaviour in the existing unit test framework.

Co-authored-by: stickies-v <stickies-v@protonmail.com>

test/lint/test_runner/src/main.rs

@@ -373,6 +373,7 @@ fn lint_std_filesystem() -> LintResult {
             "./src/",
             ":(exclude)src/ipc/libmultiprocess/",
             ":(exclude)src/util/fs.h",
+            ":(exclude)src/test/kernel/test_kernel.cpp",
         ])
         .status()
         .expect("command error")