feat: Add support for callables for TTL in Cache Handlers

[patel-vansh]

Description
This PR adds support for callable for TTL in cache handlers.

Many times the following two cases arise while calculating TTLs:

• Calculating TTL is expensive operation
• TTL depends on the return value of the callback function (for e.g, cache until the first item's expires_at is reached).

In the first senario, calculating TTL everytime, even if its a cache hit, is redundant. And in second senario, you can't just use the remember() method. You have to rely on traditional get()/save() methods.

This PR solves both problems by adding support for callables as TTL. The passed callable may optionally accept the computed value as first parameter which solves the second senario.
And by passing callable without any parameter just defers calculating TTL until cache miss.

This can be considered as a Breaking Change as the Interface method's signature is changed. However, the usage of remember() method remains mostly unchanged.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[michalsn]

Suggested change

	- **Cache:** ``CodeIgniter\Cache\CacheInterface::remember()`` now accepts a TTL callable. All built-in cache handlers inherit this method via ``BaseHandler``, so no changes are required for them.
	- **Cache:** ``CodeIgniter\Cache\CacheInterface::remember()`` now accepts a TTL callable. Custom implementations of ``CacheInterface`` must update the ``$ttl`` parameter type from ``int`` to `callable|int``.