RFR: 7262: Add rule for when the JVM version is < OpenJDK 8u302 [v6]

[Oskar Jung]

> This PR contains a rule for notifying users of JVM < OpenJDK8u302 to upgrade to avoid performance issues caused by https://bugs.openjdk.java.net/browse/JDK-8266723.
> 
> **JFR recorded on OpenJDK 8u302 EA:**
> ![Screen Shot 2021-06-02 at 14 45 46](https://user-images.githubusercontent.com/1101441/120482697-a9c7bf80-c3b1-11eb-83e0-7d17b23cfd99.png)
> 
> **JFR recorded on OpenJDK 8u292:**
> ![Screen Shot 2021-06-02 at 15 49 14](https://user-images.githubusercontent.com/1101441/120492943-ce746500-c3ba-11eb-999c-e75bf3fba245.png)

Oskar Jung has updated the pull request incrementally with one additional commit since the last revision:

  fixup! 7262: Add rule for when the JVM version is < OpenJDK 8u302

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

Changes:
  - all: https://git.openjdk.java.net/jmc/pull/256/files
  - new: https://git.openjdk.java.net/jmc/pull/256/files/8a895645..097ecc12

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmc&pr=256&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jmc&pr=256&range=04-05

  Stats: 8 lines in 1 file changed: 0 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/jmc/pull/256.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/256/head:pull/256

PR: https://git.openjdk.java.net/jmc/pull/256