chore: prepare v0.4.8 release

[emidoots]

Motivation

Cut new release, particularly for #256 which is currently blocking a major SCIP consumer.

This also helps #253

Test plan

This PR supersedes #248

In that PR, we had deferred the release due to some concerns, specifically:

1. fix: avoid overlapping definition for T::Enum synthetic serialize() method #246 added questionable T::Enum behavior.
2. ..but I investigated and found that Revert "fix: avoid overlapping definition for T::Enum synthetic serialize() method" #249 subsequently reverted it completely.
3. Current master therefore retains the old T::Enum behavior.
4. chore: Prepare for v0.4.8 release #248 predates that revert and is stale. This PR supersedes it.
5. Ultimately, since v0.4.7, the only meaningful indexer behavior remaining on master is enclosing_range from Populate enclosing_range on SCIP definition Occurrences #250 (Populate enclosing_range on SCIP definition Occurrences #250), which has tests.