CI: add coverity scheduled workflow

[chipitsine]

please find a scheduled coverity scan workflow

1. I hope it is considered useful
2. I hope that someone has admin access to https://scan.coverity.com/projects/freerdp
3. token must be copied from coverity to COVERITY_SCAN_TOKEN secret
4. coverity wants valid email (I specified "someone@example.com")

thanks for attention ))

[freerdp-bot]

Can one of the admins verify this patch?

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[akallabeth]

will check tomorrow regarding the credentials. someone in the project has them, but as you can see they have not been used for quite some time (before I joined the project actually 😁 )

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[akallabeth]

so, now we recovered the credentials, they were buried deep 😁

a few more changes and we can merge and do a first test upload!

[github-actions]

clang-tidy review says "All clean, LGTM! 👍"

[akallabeth]

LGTM

[akallabeth]

@freerdp-bot test

[freerdp-bot]

Refer to this link for build results (access rights to CI server needed):
https://ci.freerdp.com//job/PullRequestTester/11738/