Be more careful in handling unconfigured programs in the program database

[sheaf]

This PR contains several commits that address problems with how we were handling unconfigured programs in the program database:

• We should configure unconfigured programs before serialising them (using the Binary ProgramDb instance) in Distribution.Client.ProjectPlanning.configureCompiler, as otherwise we can accidentally discard information. Not doing so can lead to situations in which we can build a package just fine, but if we re-start a build we will fail, because the program database on disk stored after configuring doesn't match the program database in memory.
• As a follow-on from the above, configureRequiredProgram needs to gracefully handle an already-configured program. Not doing so means we would fall back to the simpleProgram treatment, which can cause Cabal to fail to configure a program such as hsc2hs which has custom logic for parsing its version number.
• When compiling a Setup executable, we would pass a program database for use of the stripExe command. However, the strip program might not be configured in this program database; so we make sure to configure it (in the correct environment).

Template Α: This PR modifies behaviour or interface.

TODO:

• [x] Patches conform to the coding conventions.
• [x] Any changes that could be relevant to users have been recorded in the changelog.
• [x] The documentation has been updated.
• [x] Tests have been added.

[alt-romes]

I've been trying to construct a test for these hard to trigger bugs, but I was unable to. I think it would be reasonable to move forward with this even if there are no tests given the difficulty in defining a test case for these properties.

[alt-romes]

I recall this was quite a good patch. Could anyone please review? @andreabedini @Mikolaj

[geekosaur]

@mergify backport 3.12

[mergify[bot]]

backport 3.12

✅ Backports have been created

• #10349 Be more careful in handling unconfigured programs in the program database (backport #9967) has been created for branch 3.12 but encountered conflicts