This commit introduces the "SortedDirectories" amendment, which
addresses two distinct issues:
First, it corrects a technical flaw that could, in some edge cases,
prevent an empty intermediate page from being deleted.
Second, it sorts directory entries within a page (other than order
book page entries, which remain strictly FIFO). This makes insert
operations deterministic, instead of pseudo-random and reliant on
temporal ordering.
Lastly, it removes the ability to perform a "soft delete" where
the page number of the item to delete need not be known if the
item is in the first 20 pages, and enforces a maximum limit to
the number of pages that a directory can span.
Enable all supported amendments in Env by default. Rename `features()`
to `with_features()` and add `all_features_except()` to support feature
subsets in Env. Refactor internal feature handling based on a bitset.
Add envconfig test helper for manipulating Env config via
callables. Create new common modifiers for non-admin config,
validator config and one for using different server port values.
When started with "--start", put all known, non-vetoed
amendments in the genesis ledger. This avoids the need
to wait 256 ledgers before amendments are enabled when
testing with a fresh ledger.
