Emit spec compliant QIR

[swernli]

This updates the QIR code generation logic to comply with the Base and Adaptive Profile specifications. In particular, it makes the following updates:

• The entry point function returns i64.
• Module level flags for computation extensions are updated to be consistent with spec fixes for LLVM flags.
• QIR now includes global strings in the data section that are used as tags for the output recording calls, with tag values chosen to be consistent with the Azure Quantum service output translation.
• The __quantum__qis__read_result__body function is renamed to __quantum__rt__read_result.
• Every program begins with a call to the __quantum__rt__initialize function.

[swernli]

Of note, in case it is helpful for review, the first five commits correspond (mostly) to the bullet points in the description. Commits after that may cover other integration work.