RFR: 8263790: C2: new igv_print_immediately() for debugging purpose

[Yi Yang]

Add a new igv_print_immediately, it prints the current method immediately. This differs from other igv_print* methods, it creates a well-formed and complete ideal graph xml immediately, while others accomplish their ideal graph xml when VM exists (i.e. destructor of `IdealGraphPrinter::_xx_printer`). If VM crashes before VM exit, the ideal graph xml will be ill-formed, this is fairly a common case when debugging another crash.

Test manually!

Cheers,
Yang

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Commit messages:
 - new igv_print_immediately()

Changes: https://git.openjdk.java.net/jdk/pull/3071/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3071&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263790
  Stats: 36 lines in 4 files changed: 34 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3071.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3071/head:pull/3071

PR: https://git.openjdk.java.net/jdk/pull/3071