[clang] [clang][Analyzer] Move checker 'alpha.unix.Errno' to 'unix.Errno'. (PR #69469)

[Balázs Kéri via cfe-commits]

balazske wrote:

This checker was dependent on `unix.StdCLibraryFunctions`. After that checker was moved out of alpha, it is possible to move `alpha.unix.Errno` out of alpha.
The checker was tested first on the following projects. The following links were automatically generated to compare the checker results before and after the change. What matters only is the "new reports" where the reports from the checker are shown with the new name (and in the "lost reports" with the old name), there should be no other difference. I did not find obvious false positives, and there are not many results. Most interesting are the cases found in `postgres`, even these do not look as false positive. (The checker assumes that functions like `fwrite` may write 0 bytes and return 0 if the number to write is 1, and this is different from failure of the function when it returns -1.)


memcached_1.6.8_errno_alpha_unix_vs_memcached_1.6.8_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=memcached_1.6.8_errno_alpha_unix&newcheck=memcached_1.6.8_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=memcached_1.6.8_errno_alpha_unix&newcheck=memcached_1.6.8_errno_unix&is-unique=on&diff-type=Resolved)
tmux_2.6_errno_alpha_unix_vs_tmux_2.6_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=tmux_2.6_errno_alpha_unix&newcheck=tmux_2.6_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=tmux_2.6_errno_alpha_unix&newcheck=tmux_2.6_errno_unix&is-unique=on&diff-type=Resolved)
curl_curl-7_66_0_errno_alpha_unix_vs_curl_curl-7_66_0_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=curl_curl-7_66_0_errno_alpha_unix&newcheck=curl_curl-7_66_0_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=curl_curl-7_66_0_errno_alpha_unix&newcheck=curl_curl-7_66_0_errno_unix&is-unique=on&diff-type=Resolved)
twin_v0.8.1_errno_alpha_unix_vs_twin_v0.8.1_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=twin_v0.8.1_errno_alpha_unix&newcheck=twin_v0.8.1_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=twin_v0.8.1_errno_alpha_unix&newcheck=twin_v0.8.1_errno_unix&is-unique=on&diff-type=Resolved)
vim_v8.2.1920_errno_alpha_unix_vs_vim_v8.2.1920_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_errno_alpha_unix&newcheck=vim_v8.2.1920_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_errno_alpha_unix&newcheck=vim_v8.2.1920_errno_unix&is-unique=on&diff-type=Resolved)
openssl_openssl-3.0.0-alpha7_errno_alpha_unix_vs_openssl_openssl-3.0.0-alpha7_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=openssl_openssl-3.0.0-alpha7_errno_alpha_unix&newcheck=openssl_openssl-3.0.0-alpha7_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=openssl_openssl-3.0.0-alpha7_errno_alpha_unix&newcheck=openssl_openssl-3.0.0-alpha7_errno_unix&is-unique=on&diff-type=Resolved)
sqlite_version-3.33.0_errno_alpha_unix_vs_sqlite_version-3.33.0_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=sqlite_version-3.33.0_errno_alpha_unix&newcheck=sqlite_version-3.33.0_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=sqlite_version-3.33.0_errno_alpha_unix&newcheck=sqlite_version-3.33.0_errno_unix&is-unique=on&diff-type=Resolved)
ffmpeg_n4.3.1_errno_alpha_unix_vs_ffmpeg_n4.3.1_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=ffmpeg_n4.3.1_errno_alpha_unix&newcheck=ffmpeg_n4.3.1_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=ffmpeg_n4.3.1_errno_alpha_unix&newcheck=ffmpeg_n4.3.1_errno_unix&is-unique=on&diff-type=Resolved)
postgres_REL_13_0_errno_alpha_unix_vs_postgres_REL_13_0_errno_unix	[New reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=postgres_REL_13_0_errno_alpha_unix&newcheck=postgres_REL_13_0_errno_unix&is-unique=on&diff-type=New)	[Lost reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=postgres_REL_13_0_errno_alpha_unix&newcheck=postgres_REL_13_0_errno_unix&is-unique=on&diff-type=Resolved)

https://github.com/llvm/llvm-project/pull/69469