RFR: 7903758: jextract should avoid temporary file creation [v7]

[Athijegannathan Sundararajan]

> jextract creates a temporary file to support multiple headers and special header syntax <foo.h>. This patch avoids that temporary file creation by using clang's in-memory parsing API clang_createTranslationUnitFromSourceFile

Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last revision:

  removed parseTU, parse variants that do not accept file content (review comments)

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Changes:
  - all: https://git.openjdk.org/jextract/pull/251/files
  - new: https://git.openjdk.org/jextract/pull/251/files/6b22878d..ba2104f1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jextract&pr=251&range=06
 - incr: https://webrevs.openjdk.org/?repo=jextract&pr=251&range=05-06

  Stats: 32 lines in 1 file changed: 0 ins; 24 del; 8 mod
  Patch: https://git.openjdk.org/jextract/pull/251.diff
  Fetch: git fetch https://git.openjdk.org/jextract.git pull/251/head:pull/251

PR: https://git.openjdk.org/jextract/pull/251