BLF: Optimize text rendering and caching

The current code allocates and transfers a lot of memory to the GPU,
but only a small portion of this memory is actually used.
In addition, the code calls many costly gl operations during the
caching process.

This commit significantly reduce the amount of memory by allocating
and transferring a flat array without pads to the GPU.
It also calls as little as possible the gl operations during the cache.

This code also simulate a billinear filter `GL_LINEAR` using a 1D texture.

**Average drawing time:**
|before:|0.00003184 sec
|now:|0.00001943 sec
|fac:|1.6385156675048407

**5 worst times:**
|before:|[0.001075, 0.001433, 0.002143, 0.002915, 0.003242]
|now:|[0.00094, 0.000993, 0.001502, 0.002284, 0.002328]

Differential Revision: https://developer.blender.org/D6886

Fix regression in the orientation of transform Redo operations

Caused by rBb3abd2e102df

Cleanup: Move transform_mode_init to transform_mode API

Fix T74044: Switching from Edge Slide to Move and Cancelling causes crash

`TFM_TRANSLATION` was removed in rBa33b261473e9 but is still needed.

Transform: Fix reinitialization of custom data correction

Fix transform 'center_override' not being flagged

Problem introduced by rBa33b261473e9

Fix T68878: Update shapekeys during transformation

Only use the hack in `key_block_get_data` for the bmesh shapekey.
The remaining shapekeys can use the original offset values.

Differential Revision: https://developer.blender.org/D6516

Fix T65640: Axis of Custom Shape Bones are drawn in a wrong position.

The problem is that Custom Shape Bones can also have a custom size.
So the pchan->disp_mat doesn't always consider the actual length of the bone.
The proposed solution is to calculate the axes matrix at the drawing pass.

Ref T65640

Reviewed By: fclem

Differential Revision: http://developer.blender.org/D5049

Fix T73853: Redo does't work properly with NLA "Move" transform mode

The orientation matrix when re-doing some transform operations was negated.
Thanks @lichtwerk for pointing out the problem.

Fix T71455, T73852, T73860: Transform, Redo doesn't work properly in time editors

The redo panel does not consider the position of the mouse.
So it is not possible to know the direction to redo the operator.

The solution is to add a new `direction` parameter that can be
saved and used for redo.

Differential Revision: https://developer.blender.org/D6852