[VFX] 10.x.x backports

[julienf-unity]

Purpose of this PR

Fixed:

• Target GameObject attach button does not allow attaching a valid VFX if the last selection was invalid. Case 1312178
• Deleting flow edge between Init and Update throw an invalid opeation exception Case 1315593
• Having more than five GPU Event output leads to "unexpected token 'if" at compilation Case 1323434
• Deleted properties still show up in the inspector Case 1320952
• Regression with some settings not always triggering a recompilation Case 1322844
• Exception in VFXFilterWindow if search field is empty Case 1235269

• Some doc updates

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Testing status

Test green locally

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Comments to reviewers

Notes for the reviewers you have assigned.

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[gabrieldelacruz]

The fix for Case 1323434 (Having more than five GPU Event output leads to "unexpected token 'if" at compilation) is generating some warnings. Earlier this week we discussed a different fix, replacing "i{0}" by "i_{0}" instead of "i". Maybe is a good time to do the change here?
I created a different PR for vfx/staging

[julienf-unity]

The fix for Case 1323434 (Having more than five GPU Event output leads to "unexpected token 'if" at compilation) is generating some warnings. Earlier this week we discussed a different fix, replacing "i{0}" by "i_{0}" instead of "i". Maybe is a good time to do the change here?
I created a different PR for vfx/staging

Ok I copied the changed line and commit