Readme templates should automatically determine support status from version

[lbussell]

See #6762 (review)

The support status of various .NET releases is listed in the featured tags section of each repo's README:

dotnet-docker/README.sdk.md

Lines 3 to 10 in 2a6f35b

	## Featured Tags
	* `10.0` (Release Candidate)
	* `docker pull mcr.microsoft.com/dotnet/sdk:10.0`
	* `9.0` (Standard Support)
	* `docker pull mcr.microsoft.com/dotnet/sdk:9.0`
	* `8.0` (Long-Term Support)
	* `docker pull mcr.microsoft.com/dotnet/sdk:8.0`

That status is hard-coded in the following template:

https://github.com/dotnet/dotnet-docker/blob/2a6f35b9361d1aacb664b0ce09e529698b622d2b/eng/readme-templates/FeaturedTags.md

However, we could compute it automatically. The following logic would work for this (pseudocode):

if build version contains "alpha" -> "(Alpha)"
if build version contains "preview" -> "(Preview)"
if build version contains "rc" -> "(Release Candidate)"
else ->
    if major version is even -> "(Long-Term Support)"
    else -> "(Standard Support)"

[lbussell]

[Triage] Related: official .NET support policy