RFR: 8310027: Fix -Wconversion warnings in nmethod and compiledMethod related code

[Vladimir Kozlov]

On Thu, 15 Jun 2023 22:49:36 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> This change adds casts to nmethod and compiled method offset and size functions that return int, and checked_casts where it's not obvious or already checked that the cast is correct.
> Tested with tier1 on Oracle platforms, and tier1-4 linux and windows.

Looks good.

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Marked as reviewed by kvn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14505#pullrequestreview-1483641236