[php-src] Issue #21324: PDO\SQLite: add support for session extension

Issue: https://github.com/php/php-src/issues/21324
Author: bohwaz

### Description

The session extension of SQLite provides support for creating changesets and reverting changes to a database: https://sqlite.org/sessionintro.html

Very useful for managing an app database.

It is currently enabled by default in Debian at least.

The best action would probably be to create a new PDO\SQLite\Session class:

```
PDO\SQLite\Session::__construct(PDO\SQLite $db, string $dbname = 'main')
PDO\SQLite\Session::attach(?string $table): void // pass null to attach all tables of the database
PDO\SQLite\Session::enable(?bool $enable): bool // pass null to return current enabled status
PDO\SQLite\Session::changeset(): PDO\SQLite\Session\Changeset
PDO\SQLite\Session::isEmpty(): bool
PDO\SQLite\Session::diff(string $table, string $dbname = 'main'): void
```

Deleting the session (sqlite3session_delete) would be handled when the Session object is unloaded from memory.

Starting a session would throw an exception if the session extension is not available.

By default, __construct would set `SQLITE_SESSION_OBJCONFIG_ROWID`  so that even if tables don't have a primary key they could see their changes recorded.

Here are the methods of a changeset:

```
PDO\SQLite\Session\Changeset::__construct()
PDO\SQLite\Session\Changeset::invert(): void
PDO\SQLite\Session\Changeset::load(?string $serialized_changeset = null): void // Loads an existing serialized changeset
PDO\SQLite\Session\Changeset::iterate(): Generator // iterates, for each iteration, return Change object
PDO\SQLite\Session\Changeset::__toString(): string // serialize the changeset
PDO\SQLite\Session\Changeset::add(PDO\SQLite\Session\Changeset): void // Add a changeset to another one: sqlite3changegroup_add
PDO\SQLite\Session\Changeset::addChange(PDO\SQLite\Session\Change): void // Add a single change: sqlite3changegroup_add_change
PDO\SQLite\Session\Changeset::apply(PDO\SQLite $db, ?callable $filter_callback = null, ?callable $conflict_callback = null)
PDO\SQLite\Session\Change {
  string $table;
  int $operation;
  bool $indirect;
  public function new(): array // return new values
  public function old(): array // return old values
}
```

I'm not sure about the interface of the Change object though. Probably needs more work and thought.