Simplify depth reprojection code

[Flarkk]

This PR rewrites ndc-to-view space depth reprojection code in all effects and environment shaders : GI, SSS, SSR, SSIL, SSAO, SS downsampler, Bokeh, Copy effects and Cubemap to DP

The new code typically looks like this :

float depth = texture(source_depth, uv).r;
depth = (proj_zw[1][0] - proj_zw[1][1] * depth) / (proj_zw[0][1] * depth - proj_zw[0][0]);
// with `proj_zw` a `mat2` that is the bottom-right 2x2 corner of the projection matrix.

It replaces old reprojection code which typically looks like that :

float depth = texture(source_depth, uv).r;
depth = depth * 2.0 - 1.0;
if (is_orthogonal) {
	depth = ((depth + (z_far + z_near) / (z_far - z_near)) * (z_far - z_near)) / 2.0;
} else {
	depth = 2.0 * z_near * z_far / (z_far + z_near - depth * (z_far - z_near));
}

There are some slight variations depending on whether the shader expects negative or positive depth, and whether the ndc depth is reversed.

Benefits

1. The new code doesn't depend on camera attributes anymore, which avoids issues under certain circumstances.

Camera attributes are typically retrieved from the projection matrix (with Projection::is_orthogonal(), Projection::get_z_far(), ...) then passed to the shaders.
The above functions can break under certain circumstances.
Typically when zfar is much bigger than znear, the perspective matrix that derives from it is infinite, then it becomes mathematically impossible to retrieve zfar back.

This change is part of the groundwork I'm carrying out to support wider ranges of zfar / znear ratios in single precision (today limited to ~1e6, typically zfar = 10km with znear = 0.01) which is important in open worlds and space games.

2. It prepares the support of custom projection matrices where it cannot be determined whether the projection is orthographic (for example with blended perspective and orthographic projections)

Non-regression tests

Test project : reprojection.zip

There shouldn't be any visual change after this PR except for SSS, which is broken in master (see #99220 - this PR fixes it too). The screen captures for SSS below are made with 4.2. [edit : #99220 was merged]

Visual reference before this PR (all visuals do match after the PR - see test project) :

	GI	SSS	SSR	SSIL	SSAO	Bokeh	Sky	Shadows
Persp
Ortho

[Flarkk]

Rebased on top of #99220

[Flarkk]

Rebased