basic features: convert to matrix

[ghost]

What is changed, added or deleted? (Required)

This converts the basic features that TiDB supports to a matrix, similar to the one at https://www.postgresql.org/about/featurematrix/

Additional features can be added over time, the initial set is a little bit arbitrary.

It will likely cause version-specific issues because some of the linked files may not exist, so the links will either need to be removed or changed the exact version one.

Which TiDB version(s) do your changes apply to? (Required)

• master (the latest development version)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Have version specific changes
• Might cause conflicts

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, PTAL.

[zz-jason]

LGTM

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, PTAL.

[ghost]

@zz-jason AFAIU if something is planned for GA (but not currently), we should call it planned or experimental. This helps address this style nit @TomShawn made me aware of:

https://developers.google.cn/style/future

I think logically it makes sense too. When a feature is documented as if it is there, it can create a very frustrating user experience. For me this recently happened on: #3998

[zz-jason]

OK

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, @YiniXu9506, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, @YiniXu9506, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, @YiniXu9506, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, @YiniXu9506, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, @YiniXu9506, PTAL.

[ti-srebot]

@SunRunAway, @zz-jason, @eurekaka, @TomShawn, @YiniXu9506, PTAL.

[morgo]

I'm going to close this as stale. I will reopen a new PR to replace it.