tracing/probes: Support nested typecast

When we hit an open parenthesis right after typecast closing
parenthesis, it means we have nested typecast. This allows us to
typecast a generic data member in a structure to a pointer to
another structure.

For example, to cast a DATA_MEMBER of VAR structure to STRUCT pointer
and get MEMBER value.

  (STRUCT)(VAR->DATA_MEMBER)->MEMBER

Also, we can nest typecast.

  (STRUCT1)((STRUCT2)$ARG->FIELD2)->FIELD1

Currently the max nest level is limited to 3.

This also allows user to use typecasting for registers or stacks on
kprobe events. e.g.

  (STRUCT)(%ax)->MEMBER

  (STRUCT)($stack0)->MEMBER


Link: https://lore.kernel.org/all/178271363855.1176915.16793301788257446529.stgit@devnote2/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

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