Shadow effect blur when using an orthographic camera

[gz65555]

Describe the bug
When using an orthographic camera which position is far sway from shadow, the shadow effect will be error.

Screenshots

current:

expect:

[yangfengzzz]

It is better to desgin a new shadow algorithm for ortho condition. cascade shadow only work for perspective camera

[GuoLei1990]

It is better to desgin a new shadow algorithm for ortho condition. cascade shadow only work for perspective camera

Maybe a little hard to do this, orth camera itself is a confusing effect. In fact, The essential reason for this problem is that the object is far away, but it cannot be felt visually！Therefore, even if we cancel the cascade, the coverage of shadowmap must be from the nearplane to maxShadowdistance。

I did a little research, and I haven't found any customized solutions for orthographic cameras.

But I thought of some ways to solve this problem sideways:
Engine side:

1. Add close mode for shadowmap, close mode is more friendly to the situation of this case, and this mode is very useful in some cases, which can effectively improve the shadowmap pixel utilization

User side:

1. Turn off the cascade, for the orthographic camera, the cascade has no value
2. Since the current engine is implemented in stable mode, if the camera's far plane is far away, the near plane can also be adjusted to a larger value. Later maybe just switch to close mode.

@yangfengzzz @gz65555