refactor description of types in Atomic

[orklah]

This PR propose to refactor the description of types in Atomic.

I always thought it was messy.

For example:

• In Atomic, getId() called __toString()
• In CallableTrait, __toString() called getId()
• In TCallableString, getId() called getKey()
• In TClassString, __toString() called getKey()
• In TConditional, getKey() called __toString

Aaand I'm already lost. Adding to that the fact that no documentation exists on that, it didn't help.

What I changed:

• __toString is now final in Atomic and calls getId() with default params
• getId() has a new param $exact who defaults to true. When true, it displays the most detailed type it can, otherwise, it displays a generic version (it depends widely on each type)
• getId() now calls getKey() by default unless overrided
• I added some documentation

almost every other change is a consequence of changing the things above. Mainly:

• getId() has now two different caches in Union for exact mode and non-exact mode. This may degrade memory a little but it could gain performances (where before, calls to __toString were not cached)
• __toString used to display the non-exact type, now it calls getId() with $exact = true, so wherever I needed, I removed the implicit calls to __toString for a getId(false)
• getId() on TLiteralString was using double quotes to display the types. This is not consistent with the rest of the types (in docblock for example) so I changed that

I'm still not completely satisfied. I think there is still too many redundancy between getId(), getKey(), toNamespacedString, toPhpString. I feel we should be able to go further but it's already a big step forward

@muglug Do you think this goes in the right direction? Maybe you have special insight here? I'm not sure what getId() was supposed to be. I also have difficulties understanding when getKey should be overrided and with what value

[orklah]

@muglug do you have an opinion on this? I don't want to botch up this if it had a specific goal I'm missing...

[muglug]

Sorry, I think this is a good idea!

[muglug]

Occasionally __toString has been used for more human-readable things but I don't really think that has value now. getKey is mainly used to ensure that arrays are always stored under the same array key.

[AndrolGenhald]

@orklah Was this an intentional change? It caused one of my tests to fail when rebasing because $foo = "bar" now has type 'bar' instead of "bar". Could it affect plugins?

[orklah]

This was indeed intended. I mentionned it in the PR

getId() on TLiteralString was using double quotes to display the types. This is not consistent with the rest of the types (in docblock for example) so I changed that

I didn't thought about plugins, I'll add this in UPGRADE file

[orklah]

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