Show regression information in email reports

[gctucker]

The current email reports look like this:

On 30/05/2023 09:20, staging.kernelci.org bot wrote:
> [STAGING] mainline/master v6.4-rc4-31-g8b817fded42d: 4 runs 0 failures
> 
> Summary
> =======
> 
> Tree:     mainline
> Branch:   master
> Describe: v6.4-rc4-31-g8b817fded42d
> URL:      https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> SHA1:     8b817fded42d8fe3a0eb47b1149d907851a3c942
> Name            | Result   | Total    | Failures
> ----------------+----------+----------+---------
> kver            | pass     |        1 |        0
> kunit           | pass     |        7 |        0
> kunit-x86_64    | pass     |      723 |        2
> kbuild-gcc-10-x86 | pass     |       11 |        0
> 
> 
> Failing tests
> =============
> 
> kunit-x86_64
> ------------
> 
> * exec.input_core.input_test_match_device_id
> * exec.input_core.input_test_match_device_id

This includes a list of failing tests (which appears to be the same but listed twice here). What we really need is a list of regressions instead, to make it on part with email reports sent by the legacy system.

• Report updated to show regressions
• Tested locally
• Tested on staging