Unrevert "Bump version to 8"

[jjonescz]

Reverts #9298.
Unreverts #9258.
WebTools counterpart: https://dev.azure.com/devdiv/DevDiv/_git/WebTools/pullrequest/498945
VS insertions: Razor only, WebTools only, Razor + WebTools

[jaredpar]

I feel like this should be titled "Revert Revert Revert" 😉

[jjonescz]

VS insertion looks good. We will probably need to somehow insert both WebTools and Razor at the same time.

@dotnet/razor-compiler for reviews

[333fred]

We need to get assembly redirects into devenv so we don't need to do coordinated insertions with WebTools all the time, or this will be untenable long term. We'll need to update https://devdiv.visualstudio.com/DevDiv/_git/VS?path=/src/ProductData/AssemblyVersions.tt&version=GBmain&line=147&lineEnd=149&lineStartColumn=1&lineEndColumn=1&lineStyle=plain&_a=contents, and work with Tiger to update these versions automatically with the insertion tool.

Hopefully, with such a change, we won't need to update WebTools at all.

[DustinCampbell]

@jjonescz, @jaredpar, @333fred - is this PR still needed or can it be closed after 6 months of inactivity?

[jjonescz]

is this PR still needed or can it be closed after 6 months of inactivity?

I think we still want to change Razor's version from 7 to 8 or even 9 now. But some infra changes are needed first so the insertions handle such version changes automatically.

That being said, I will close this and open new PR bumping to version 9 when it works.