Deprecation warnings for features we plan to remove

[cameel]

We decided to introduce deprecation warnings for the following features:

• Reconsider operators on ContractType #11700
• Remove .send and .transfer. #7455
• Remove ABIEncoderV1 #11323
• Disallow internal function pointers in storage #15794
• The old optimizer breaks internal function equality #13969
• Warning about evaluation order dependent contract creation. #14459
• Insufficient check for uninitialized storage pointer access #14021
• [CLI] Drop --combined-json option and direct users to standard json #10278
• Disallow virtual modifiers #12483
• All Solidity and Yul identifiers that will become keywords (Reserve keywords and remove identifier exceptions for 0.9.0 #14770)
• Removal of support for unqualified library names (Cannot link unqualified library names via Standard JSON #12145)
• Removal of BMC from SMTChecker
• Removal of the /// @solidity memory-safe-assembly comment
• Removal of partial array assignment (assignment of a shorter array to a longer one with the rest filled with zeros). Should suggest replacing with a loop.

Some of them may be removed already in 0.9.0, for some that may be too soon, but we should start preparing the ground already to elicit some feedback and keep users aware.

[cameel]

@clonker suggests a warning for #14033 as well.

[cameel]

Regarding #14033, @ekpyron pointed out that we didn't think a deprecation warning was not necessary since there won't be much of a deprecation period until 0.9.0. Still, if we do add these warnings before 0.9.0, I think it should be included.

[cameel]

Adding #14459, #13800 and #14021 to the list. In all of them we already have a decision to issue a warning before we change or remove them in 0.9.