[release] v0.7.6

[yuanming-hu]

Related issue = #1989

Changelog:

• [workflow] Test OpenGL using GitHub actions ([workflow] Test OpenGL using GitHub actions #2014) (by Yuanming Hu)
• [cuda] Fix ti.random(dtype=ti.f64) ([cuda] Fix ti.random(dtype=ti.f64) #2042) (by Yuanming Hu)
• [opengl] [refactor] Refactor OpenGL type system to support u32 and u64 ([OpenGL] [refactor] Refactor OpenGL type system to support u32 and u64 #2027) (by 彭于斌)
• [type] Fix struct-for demotion on bit_struct SNodes ([type] Fix struct-for demotion on bit_struct SNodes #2039) (by Yuanming Hu)
• [async] More fixes of constant folding in async mode ([async] More fixes of constant folding in async mode #2035) (by Ye Kuang)
• [opt] [async] Fix constant folding in async mode ([opt] [async] Fix constant folding in async mode #2034) (by xumingkuan)

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