Improve error message in AbstractRecordAndOffset

[lbergelson]

Description

• Include the value of the offset and length in an error message so you know what the out of bounds value was.

This might help debug a bug the production team is seeing.

Things to think about before submitting:

• [ ] Make sure your changes compile and new tests pass locally.
• [ ] Add new tests or update existing ones:
  • A bug fix should include a test that previously would have failed and passes now.
  • New features should come with new tests that exercise and validate the new functionality.
• [ ] Extended the README / documentation, if necessary
• [ ] Check your code style.
• [ ] Write a clear commit title and message
  • The commit message should describe what changed and is targeted at htsjdk developers
  • Breaking changes should be mentioned in the commit message.

[codecov-commenter]

Codecov Report

Merging #1484 into master will decrease coverage by 0.002%. The diff coverage is 0.000%.

@@               Coverage Diff               @@
##              master     #1484       +/-   ##
===============================================
- Coverage     69.216%   69.214%   -0.002%     
  Complexity      8704      8704               
===============================================
  Files            588       588               
  Lines          34583     34584        +1     
  Branches        5780      5780               
===============================================
  Hits           23937     23937               
- Misses          8366      8367        +1     
  Partials        2280      2280               

Impacted Files	Coverage Δ	Complexity Δ
.../htsjdk/samtools/util/AbstractRecordAndOffset.java	80.769% <0.000%> (-3.231%)	9.000 <0.000> (ø)

[lbergelson]

@jamesemery I added the same record toString as well.

[lbergelson]

The string + operator does a null check. It's basically x == null ? "null" : x.toString()