RFR: 8350115: [leyden] Clean up name_and_sig_as_C_string uses

[Aleksey Shipilev]

Profiles show that various `name_and_sig_as_C_string` are taking about 1.2% in Leyden benchmark profiles. We should sweep those up into conditional log statements and/or common the paths where we actually need these names outside of logging. 

After this fix, the profile impact of `name_and_sig_as_C_string` is `<0.05%`.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/leyden/pull/43/files
  Webrev: https://webrevs.openjdk.org/?repo=leyden&pr=43&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350115
  Stats: 16 lines in 1 file changed: 5 ins; 3 del; 8 mod
  Patch: https://git.openjdk.org/leyden/pull/43.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/43/head:pull/43

PR: https://git.openjdk.org/leyden/pull/43