RFR: 8290834: Improve potentially confusing documentation on collection of profiling information [v7]

[Dean Long]

On Sat, 23 Jul 2022 13:59:59 GMT, Julian Waters <jwaters at openjdk.org> wrote:

>> Documentation on the MethodData object incorrectly states that it is used when profiling in tiers 0 and 1, when it only does so for tier 0 (Interpreter) and tier 3, while tier 1 (Fully optimizing C1) does not collect any profile data at all. Additionally, the description for the different execution tiers is slightly confusing. This cleanup attempts to slightly better clarify how profiling is tied together between the Interpreter and C1, explain what MDO is an abbreviation for (MethodData object), and corrects the documentation for MethodData as well.
>
> Julian Waters has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fixup

Marked as reviewed by dlong (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/9598