[SDK] support aggregation of identical instruments (#3358)

[malkia]

• use the existing storage for sync or async instruments of the same name. add tests

• add hash and name case insensitive hash for InstrumentDescriptor. Update storage registry to use the hash and equality structs. Add tests.

• don't allocate heap in the hash. fix some ci failures

• fix a few more ci failures.

• move the instrument descriptor ostream operator to meter.cc to not leak the ostream header and keep the meter instrument creation warning implementation in the same file

• adds instrument descriptor tests

• add comments

• Move case-insensitive equals method and IsDuplicate method into InstrumentDescriptorUtils struct. Add log streamable wrappers for scopes and instrument descriptors. Add tests for correcitve views for name and description duplicates

• fix iwyu errors

• duplicate instrument log message improvements to match spec. minor test additions/cleanup

• changelog entry

• address review feedback. Add Ascii to the name of the instrument util case-insensitive equal function

• address feedback: short circuit the instrument descriptor CaseInsensitiveAsciiEquals and IsDuplicate checks

• fix comments

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Fixes # (issue)

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed