RFR: 7000: Update third party library used in flightrecorder.flameview

[Guru Hb]

On Sun, 20 Dec 2020 20:37:02 GMT, Guru Hb <ghb at openjdk.org> wrote:

> Updated below listed third party library used in flameview 
> 1. d3.js (v6.3.1) : Updated Copyright notice in THIRDPARTYREADME.txt from https://raw.githubusercontent.com/d3/d3/master/LICENSE
> 2. d3-flamegraph (v4.0.6) 
> 3. d3-flamegraph-tooltip (v4.0.6) : Replaced d3-tip which is currently archived.
> 
> Note: minified version (2) and (3) doesn't render Flameview as expected, Tried debugging in Chrome with page.templated formatted and got console error "Uncaught TypeError: Cannot read property 'defaultFlamegraphTooltip' of undefined ... "
> 
> Tested on Windows, Mac OS and Ubuntu.

Updated Unit test due to two modification : 
1. Root JSON object should required value (assuming the value of 1234, Root object should have i.e "v" : 1234)
2. Value should be represented in Integer rather than String. This is due to refactoring done in d3-flamegraph https://github.com/spiermar/d3-flame-graph/commit/0ecd1904b91ae260fb1170043a8f23d04f8d5c13

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PR: https://git.openjdk.java.net/jmc/pull/186