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

[Coleen Phillimore]

> 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.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15095/files
  - new: https://git.openjdk.org/jdk/pull/15095/files/d787f46a..d1bcdc36

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15095&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15095&range=02-03

  Stats: 48 lines in 3 files changed: 13 ins; 5 del; 30 mod
  Patch: https://git.openjdk.org/jdk/pull/15095.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15095/head:pull/15095

PR: https://git.openjdk.org/jdk/pull/15095