[k2] make init instance memory size adjustable

[PetrShumilov]

Key changes:

• Set initial instance memory size to 64Mb (instead of 128 Mb previously)
• Set min instance extra memory size to 64Mb (instead of 1Mb previously)
• Made initial instance memory size adjustable via initial-instance-memory-size component argument
• Made min instance extra memory size adjustable via min-instance-extra-memory-size component argument