i#8021: Add DR options parsing in the kernel module init (#8096)

- Add an `options` module parameter to accept DynamoRIO options on
`insmod` and initialize them via `dynamorio_app_init_part_one_options()`
during module init.
- Added functions in `core/kernel_linux/os.c` that
`dynamorio_app_init_part_one_options()` depends on. They are exercised
by the init path and tested in the insmod CI.
- Implement `kernel_setenv()` for saving the options value. 
- Implement `os_check_option_compatibility()` to enforce kernel-mode
options constraints.
- Update the kernel module insmod workflow to build with both
`-DDEBUG=ON` and `OFF`, and verify that runtime options (`-loglevel 2`)
are parsed and logged correctly in the debug build.

On configuration lookup: the shared init path still performs it, but
`os_open()` is intentionally not implemented in kernel mode and returns
`INVALID_FILE` unconditionally. So no config file can be found and
options can only be set using the module parameter.

The kernel-mode options constraints implemented in
`os_check_option_compatibility()` are mostly copied from drk and may
need future adjustments. For example, #8116 tracks CPU-private fragment
restrictions (`shared_bbs`, `shared_traces`, `coarse_units`).

This initial implementation only supports setting options at module load
time. Dynamic updates and per-process options are tracked by #8115.

Issue: #8021