RFR: 8313435: Clean up unused default methods code [v4]

[Ioi Lam]

On Wed, 2 Aug 2023 18:30:58 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Default methods processing code has unused code (that gets -Wconversion warnings) from when it was used to create bridge (called overpass) method for an early implementation of generic reification in Hotspot.
>> 
>> This change removes unused bytecodeAssembler code and adds a check for methods and constant pool overflow.
>> Tested with tier1 and runtime/lambda-features tests.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Check for constant pool overflow when appending entries from default methods error (aka overpass) methods.

Looks good to me. Thanks for making the `BytecodeConstantPool::find_or_add()` method fail early so we don't have potentially invalid bytecodes in the buffer.

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Marked as reviewed by iklam (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/15095#pullrequestreview-1559843812