Add clang-tidy config file

Add clang-tidy config file

Copied from:

  https://git.lttng.org/?p=lttng-tools.git;a=blob;f=.clang-tidy;h=75f559c5d961041df8e37280ef27cb0cac8cdd96;hb=20c4b46aee1a984bc558b483826c1078f24d35e9

And adapted for Babeltrace:

 - Define `BT_ASSERT` and `BT_ASSERT_DBG` as assertion macros.
 - Remove `HeaderFilterRegex`.  We might want to use this setting, but
   I'm not sure what its value would be for Babeltrace.
 - Fix a . -> , typo

Change-Id: I73f1776bc4b7cb1bdc0d5728f9a46b17157088c8
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12078
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>