- Step interpolant now uses gl.NEAREST for texture sampler: This allows
for hard transition between different line sections when using step
interpolation. Other use cases are covered by using a smooth interpolation
type along with gl.LINEAR texture sampler.
- Step interpolant now uses an increased texture resolution color ramp
based on the total line length tile coverage to limitate the potential
precision issues for high coverage. We are still limitated by the precision
of v_lineprogress currently encoded in a 15bits floating point value.

Reuse color ramp memory placement when already available

Only calculate max distance if clipstart and clipend are defined

Increase precision of line progress when needed

Tile line gradient textures

Review comments

- Eliminate Math.log2 (not available on ie11)
- Inline and compress evaluation interpolations for line clip by
specializing it for the use case

Thanks @mourner

- Use single attribute for uv on x, move computation cpu side
- Offload fragment shader from a few operations by moving it to vertex
- More explicit addHalfVertex function block