Add argument lifetime to BaseTableExpr's evaluate

[jpschorr]

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[sadderchris]

There's also an implicit lifetime on the Cow as well (the type is actually Cow<'_, Value>). Can you check this doesn't also need to be named?

As a nit: you may want to throw #![warn(rust_2018_idioms)] or even #![deny(rust_2018_idioms)] at the top of your crates' lib.rs to enforce that lifetimes always get written out (unless you feel really strongly about the added verbosity - IMO the benefits of this lint outweigh the downsides). It's easy to forget about implicit lifetimes otherwise.

[github-actions]

Conformance comparison report

	Base (1d5bd99)	91b7325	+/-
% Passing	90.35%	90.35%	0.00%
✅ Passing	5731	5731	0
❌ Failing	612	612	0
🔶 Ignored	0	0	0
Total Tests	6343	6343	0

Number passing in both: 5731

Number failing in both: 612

Number passing in Base (1d5bd99) but now fail: 0

Number failing in Base (1d5bd99) but now pass: 0

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.25%. Comparing base (d4906a4) to head (6dc377d).

Additional details and impacted files

@@                    Coverage Diff                    @@
##           fix-basetableexpr-errors     #448   +/-   ##
=========================================================
  Coverage                     79.25%   79.25%           
=========================================================
  Files                            66       66           
  Lines                         17735    17738    +3     
  Branches                      17735    17738    +3     
=========================================================
+ Hits                          14055    14058    +3     
  Misses                         3111     3111           
  Partials                        569      569           

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