RFR: 8313435: Clean up unused default methods code [v6]

[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:

  Change to checked_cast<>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/15095/files
  - new: https://git.openjdk.org/jdk/pull/15095/files/559645d4..124d2aaf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15095&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15095&range=04-05

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 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