Add support for Skeema through `innodb_adaptive_hash_index` global system variable

[Skeema](https://www.skeema.io/), the declarative SQL-based schema management tool for MySQL/MariaDB, is currently incompatible with Dolt.

This is because in [`hydrateVars`](https://github.com/skeema/skeema/blob/5cc5cb0a5c0f18b107253c287ac9da226cd9c1dd/internal/tengo/instance.go#L384), it tries to read `innodb_adaptive_hash_index`, which fails, marking the connection as invalid.

My understanding (based on Claude research) is that it would be safe to implement this (default to on), matching other InnoDB settings that don't apply to Dolt.

Would you accept a PR to fix this? It seems an upstream fix in https://github.com/dolthub/go-mysql-server/blob/f5b97c4d91792984518b86e17f0fcee6a6a4f506/sql/variables/system_variables.go#L219 to add `innodb_adaptive_hash_index` there would be the correct fix?

Thanks.

Start in sql/variables/system_variables.go at the referenced system-variable definitions and compare nearby InnoDB settings that do not apply to Dolt. Add support for innodb_adaptive_hash_index with the proposed default, then verify that Skeema's hydrateVars lookup no longer invalidates the connection.

Written by the indexing model from the issue text.