[clang] [clang][analyzer] Move StreamChecker out of the alpha package. (PR #89247)

[Balázs Kéri via cfe-commits]

balazske wrote:

The checker is usable enough to move to non-alpha state.
This table contains some links to the results after the "Pedantic" option was added. The "new reports" are the ones that got removed if the option is turned on. At some projects there are still many results, for example at `vim`. The reason is that often read operations are not checked for error (or EOF) too, and the pedantic mode removes such warnings for the write operations only. But if read operations would be included, the checker almost loses its purpose to find unchecked operations. I think that probably this is a checker that must not be turned on by default, but still is not an alpha checker.

| Project | New Reports | Resolved Reports |
|---------|-------------|------------------|
| codechecker | [14 new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=codechecker_v6.17.0_with_pedantic_off&newcheck=codechecker_v6.17.0_with_pedantic_on&diff-type=New) | No reports 
| vim | [119 new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_with_pedantic_off&newcheck=vim_v8.2.1920_with_pedantic_on&diff-type=New) | No reports 
| sqlite | [74 new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=sqlite_version-3.33.0_with_pedantic_off&newcheck=sqlite_version-3.33.0_with_pedantic_on&diff-type=New) | No reports 
| libwebm | No reports | No reports 
| xerces | [2 new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=xerces_v3.2.3_with_pedantic_off&newcheck=xerces_v3.2.3_with_pedantic_on&diff-type=New) | No reports 
| bitcoin | [4 new reports](https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=bitcoin_v0.20.1_with_pedantic_off&newcheck=bitcoin_v0.20.1_with_pedantic_on&diff-type=New) | No reports 


https://github.com/llvm/llvm-project/pull/89247