[Arm64] Peephole optimization opportunities

[echesakov]

• ARM64: Optimize redundant memory loads with mov #35141 : Optimize redundant memory loads with mov
• ARM64 Redundant load/stores for methods that operates/returns structs #35071 : Redundant load/stores for methods that operates/returns structs
• ARM64: Optimize pair of "str wzr, [reg]" to "str xzr" #35136 : Optimize pair of "str wzr, [reg]" to "str xzr"
• ARM64: Optimize pair of "str reg, [fp]" to stp  #35134 : Optimize pair of "str reg, [fp]" to stp (Done: Replace successive "ldr" and "str" instructions with "ldp" and "stp" #77540)
• ARM64: Optimize pair of "str reg, [reg]" to stp #35133 : Optimize pair of "str reg, [reg]" to stp (WIP: PR77540)
• ARM64: Optimize pair of "ldr reg, [reg]" to ldp #35132 : Optimize pair of "ldr reg, [reg]" to ldp (WIP: PR77540)
• ARM64: Optimize pair of "ldr reg, [fp]" to ldp #35130 : Optimize pair of "ldr reg, [fp]" to ldp (WIP: PR77540)
• ARM64: Redundant movs done for zero extend the register #35254 : Redundant movs done for zero extend the register

category:cq
theme:optimization
skill-level:expert
cost:medium
impact:medium

[kunalspathak]

Moving this to Future.
cc: @a74nh