static linkage migrations

[beckermr]

We should be able to support automated rebuilds of chains of statically linked packages as follows.

In the extra section of the recipe we could ask maintainers to list the abstract requirements for any host deps that should be pinned exactly for static linking.

For example, for llvmlite we might list

extra:
  static_linking_host_requirements:
    - llvmdev 15.*
    - llvm 15.*

Then the bot would do the following computation:

1. It would download the repodata for a given plat-arch combo
2. Find the latest versions of the packages that match the static_linking_host_requirements and select the one with the highest build number.
3. Find the latest version of the package(s) built by the feedstocks, and extract from their artifacts the versions of the host deps that were used for the build.
4. If the any of the versions from 2 are bigger than those from 3 and any dependencies of the package that are also statically linked have already been migrated, then issue a PR updating the recipe with the full version and build string for the statically linked packages.

So for llvmlite the net result would be an update to the recipe that looks like

 host:
   - blah blah blah
-  - llvmdev 15.0.6 h145432df_6  # [linux and x86]
-  - llvm 15.0.6 h363daef_6      # [linux and x86]
+  - llvmdev 15.0.7 h124432df_6  # [linux and x86]
+  - llvm 15.0.7 haE3567daef_6   # [linux and x86]